The World as Will and Representation/First Half

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Supplements to the First Book,

"'Warum willst du dich von uns Allen
Und unsrer Meinung entfernen?'
Ich schreibe nicht euch zu gefallen,
Ihr sollt was lernen."




First Half




IN boundless space countless shining spheres, about each of which, and illuminated by its light, there revolve a dozen or so of smaller ones, hot at the core and covered with a hard, cold crust, upon whose surface there have been generated from a mouldy film beings which live and know this is what presents itself to us in experience as the truth, the real, the world. Yet for a thinking being it is a precarious position to stand upon one of those numberless spheres moving freely in boundless space without knowing whence or whither, and to be only one of innumerable similar beings who throng and press and toil, ceaselessly and quickly arising and passing away in time, which has no beginning and no end ; moreover, nothing permanent but matter alone and the recurrence of the same varied organised forms, by means of certain ways and channels which are there once for all. All that empirical science can teach is only the more exact nature and law of these events. But now at last modern philosophy, especially through Berkeley and Kant, has called


to mind that all this is first of all merely a phenomenon of the brain, and is affected with such great, so many, and such different subjective conditions that its supposed absolute reality vanishes away, and leaves room for an entirely different scheme of the world, which consists of what lies at the foundation of that phenomenon, i.e., what is related to it as the thing in itself is related to its mere manifestation.

"The world is my idea" is, like the axioms of Euclid, a proposition which every one must recognise as true as soon as he understands it ; although it is not a proposition which every one understands as soon as he hears it. To have brought this proposition to clear consciousness, and in it the problem of the relation of the ideal and the real, i.e., of the world in the head to the world outside the head, together with the problem of moral freedom, is the distinctive feature of modern philosophy. For it was only after men had spent their labour for thousands of years upon a mere philosophy of the object that they discovered that among the many things that make the world so obscure and doubtful the first and chiefest is this, that however immeasurable and massive it may be, its existence yet hangs by a single thread ; and this is the actual consciousness in which it exists. This condition, to which the existence of the world is irrevocably subject, marks it, in spite of all empirical reality, with the stamp of ideality, and therefore of mere phenomenal appearance. Thus on one side at least the world must be recognised as akin to dreams, and indeed to be classified along with them. For the same function of the brain which, during sleep, conjures up before us a completely objective, perceptible, and even palpable world must have just as large a share in the presentation of the objective world of waking life. Both worlds, although different as regards their matter, are yet clearly moulded in the one form. This form is the intellect, the function of the brain. Descartes was probably the first who attained to the


degree of reflection which this fundamental truth de mands, and consequently he made it the starting-point of his philosophy, though provisionally only in the form of a sceptical doubt. When he took his cogito ergo sum as alone certain, and provisionally regarded the existence of the world as problematical, he really dis covered the essential and only right starting-point of all philosophy, and at the same time its true foundation. This foundation is essentially and inevitably the subjective, the individual consciousness. For this alone is and remains immediate ; everything else, whatever it may be, is medi ated and conditioned through it, and is therefore depen dent upon it. Therefore modern philosophy is rightly regarded as starting with Descartes, who was the father of it. Not long afterwards Berkeley followed the same path further, and attained to idealism proper, i.e., to the knowledge that the world which is extended in space, thus the objective, material world in general, exists as such simply and solely in our idea, and that it is false, and indeed absurd, to attribute to it, as such, an existence apart from all idea and independent of the knowing sub ject, thus to assume matter as something absolute and possessed of real being in itself. But his correct and pro found insight into this truth really constitutes Berkeley s whole philosophy ; in it he had exhausted himself.

Thus true philosophy must always be idealistic ; indeed, it must be so in order to be merely honest. For nothin^ is more certain than that no man ever came out of him self in order to identify himself directly with things which are different from him ; but everything of which he has certain, and therefore immediate, knowledge lies within his own consciousness. Beyond this consciousness, therefore, there can be no immediate certainty ; but the first principles of a science must have such certainty. For the empirical standpoint of the other sciences it is quite right to assume the objective world as something absolutely given ; but not so for the standpoint of philo-


sophy, which has to go back to what is first and original. Only consciousness is immediately given; therefore the basis of philosophy is limited to facts of consciousness, i.e., it is essentially idealistic. Realism which commends it self to the crude understanding, by the appearance which it assumes of being matter-of-fact, really starts from an arbitrary assumption, and is therefore an empty castle in the air, for it ignores or denies the first of all facts, that all that we know lies within consciousness. For that the objective existence of things is conditioned through a subject whose ideas they are, and consequently that the objective world exists only as idea, is no hypothesis, and still less a dogma, or even a paradox set up for the sake of discussion ; but it is the most certain and the simplest truth ; and the knowledge of it is only made difficult by the fact that it is indeed so simple, and that it is not every one who has sufficient power of reflection to go back to the first elements of his consciousness of things. There can never be an absolute and independent objective exis tence ; indeed such an existence is quite unintelligible. For the objective, as such, always and essentially has its existence in the consciousness of a subject, is thus the idea of this subject, and consequently is conditioned by it, and also by its forms, the forms of the idea, which depend upon the subject and not on the object.

That the objective world would exist even if there existed no conscious being certainly seems at the first blush to be unquestionable, because it can be thought in the ab stract, without bringing to light the contradiction which it carries within it. But if we desire to realise this abstract thought, that is, to reduce it to ideas of perception, from which alone (like everything abstract) it can have con tent and truth, and if accordingly we try to imagine an objective world ivithout a knowing subject, we become aware that what we then imagine is in truth the opposite of what we intended, is in fact nothing else than the process in the intellect of a knowing subject who perceives an


objective world, is thus exactly what we desired to exclude. For this perceptible and real world is clearly a pheno menon of the brain ; therefore there lies a contradiction in the assumption that as such it ought also to exist in dependently of all brains.

The principal objection to the inevitable and essential ideality of all objects, the objection which, distinctly or in distinctly, arises in every one, is certainly this : My own person also is an object for some one else, is thus his idea, and yet I know certainly that I would continue to exist even if he no longer perceived me. But all other objects also stand in the same relation to his intellect as I do ; consequently they also would continue to exist \vithout being perceived by him. The answer to this is: That other being as whose object I now regard my person is not absolutely the subject, but primarily is a knowing individual. Therefore, if he no longer existed, nay, even if there existed no other conscious being except myself, yet the subject, in whose idea alone all objects exist, would by no means be on that account abolished. For I myself indeed am this subject, as every conscious being is. Consequently, in the case assumed, my person would certainly continue to exist, but still as idea, in my own knowledge. For even by me myself it is always known only indirectly, never immediately ; because all existence as idea is indirect. As object, i.e., as extended, occupying space and acting, I know my body only in the perception of my brain. This takes place by means of the senses, upon data supplied by which the percipient understanding- performs its function of passing from effect to cause, and thereby, in that the eye sees the body or the hands touch it, it constructs that extended figure which presents itself in space as my body. By no means, however, is there directly given me, either in some general feeling of bodily existence or in inner self-consciousness, any extension, form, or activity, which would then coincide with my nature itself, which accordingly, in order so to exist, would require no


other being in whose knowledge it might exhibit itself. On the contrary, that general feeling of bodily existence, and also self-consciousness, exists directly only in relation to the will, that is, as agreeable or disagreeable, and as active in the acts of will, which for external perception exhibit themselves as actions of the body. From this it follows that the existence of my person or body as something extended and acting always presupposes a Jcnoiving being distinct from it ; because it is essentially an existence in apprehension, in the idea, thus an existence for another. In fact, it is a phenomenon of brain, just as much whether the brain in which it exhibits itself is my own or belongs to another person. In the first case one s own person divides itself into the knowing and the known, into object and subject, which here as everywhere stand opposed to each other, inseparable and irreconcilable. If, then, my own person, in order to exist as such, always requires a knowing subject, this will at least as much hold good of the other objects for which it was the aim of the above objection to vindicate an existence independent of know ledge and its subject.

However, it is evident that the existence which is con ditioned through a knowing subject is only the existence in space, and therefore that of an extended and active being. This alone is always something known, and con sequently an existence for another. On the other hand, every being that exists in this way may yet have an existence for itself, for which it requires no subject. Yet this existence for itself cannot be extension and activity (together space-occupation), but is necessarily a being of another kind, that of a thing in itself, which, as such, can never be an object. This, then, would be the answer to the leading objection set forth above, which accordingly does not overthrow the fundamental truth that the objectively given world can only exist in the idea, thus only for a subject.

We have further to remark here that Kant also, so Ion*?


at least as he remained consistent, can have thought no


objects among his things in themselves. For this follows from the fact that he proves that space, and also time, are mere forms of our perception, which consequently do not belong to things in themselves. What is neither in space nor in time can be no object ; thus the being of things in themselves cannot be objective, but of quite a different kind, a metaphysical being. Consequently that Kantian principle already involves this principle also, that the objective world exists only as idea.

In spite of all that one may say, nothing is so per sistently and ever anew misunderstood as Idealism, because it is interpreted as meaning that one denies the empirical reality of the external world. Upon this rests the per petual return to the appeal to common sense, which appears in many forms and guises ; for example, as an " irresistible conviction " in the Scotch school, or as Jacobi s faith in the reality of the external world. The external world by no means presents itself, as Jacobi declares, upon credit, and is accepted by us upon trust and faith. It presents itself as that which it is, and per forms directly what it promises. It must be remembered that Jacobi, who set up such a credit or faith theory of the world, and had the fortune to impose it upon a few pro fessors of philosophy, who for thirty years have philoso phised upon the same lines lengthily and at their ease, is the same man who once denounced Lessing as a Spino/ist, and afterwards denounced Schelling as an atheist, and who received from the latter the well-known and well- deserved castigation. In keeping with such zeal, when he reduced the external world to a mere matter of faith he only wished to open the door to faith in general, and to prepare belief for that which was afterwards really to be made a matter of belief ; as if, in order to introduce a paper currency, one should seek to appeal to the fact that the value of the ringing coin also depends merely on the stamp which the State has set upon it. Jacobi, in his doctrine that the reality of the external world is assumed


upon faith, is just exactly " the transcendental realist who plays the empirical idealist" censured by Kant in the " Critique of Pure Reason," first edition, p. 369.

The true idealism, on the contrary, is not the empirical but the transcendental. This leaves the empirical reality of the world untouched, but holds fast to the fact that every object, thus the empirically real in general, is conditioned in a twofold manner by the subject ; in the first place materially or as object generally, because an objective existence is only conceivable as opposed to a subject, and as its idea; in the second place formally, because the mode of existence of an object, i.e., its being perceived (space, time, causality), proceeds from the subject, is pre arranged in the subject. Therefore with the simple or Berkeleian idealism, which concerns the object in general, there stands in immediate connection the Kantian idealism, which concerns the specially given mode or manner of objective existence. This proves that the whole material world, with its bodies, which are extended in space and, by means of time, have causal relations to each other, and everything that depends upon this that all this is not something which is there independently of our head, but essentially presupposes the functions of our brain by means of which and in which alone such an objective arrangement of things is possible. For time, space, and causality, upon which all those real and objective events rest, are them selves nothing more than functions of the brain ; so that thus the unchangeable order of things which affords the criterion and clue to their empirical reality itself proceeds only from the brain, and has its credentials from this alone. All this Kant has expounded fully and thoroughly ; only he does not speak of the brain, but calls it " the faculty of knowledge." Indeed he has attempted to prove that when that objective order in time, space, causality, matter, &c., upon which all the events of the real world ultimately rest, is properly considered, it cannot even be conceived as a self-existing order, i.e., an order of the thing in itself,


or as something absolutely objective and unconditionally given, for if one tries to think this out it leads to contra dictions. To accomplish this was the object of the anti nomies, but in the appendix to my work I have proved the failure of the attempt. On the other hand, the Kantian doctrine, even without the antinomies, leads to the insight that things and the whole mode of their existence are inseparably bound up with our consciousness of them. Therefore whoever has distinctly grasped this soon attains to the conviction that the assumption that things also exist as such, apart from and independently of our con sciousness, is really absurd. That we are so deeply in volved in time, space, causality, and the whole regular process of experience which rests upon them, that we (and indeed the brutes) are so perfectly at home, and know how to find our way from the first this would not be possible if our intellect were one thing and things another, but can only be explained from the fact that both con stitute one whole, the intellect itself creates that order, and exists only for things, while they, on the other hand, exist only for it.

But even apart from the deep insight, which only the Kantian philosophy gives, the inadmissibility of the assumption of absolute realism which is so obstinately clung to may be directly shown, or at least made capable of being felt, by the simple exhibition of its meaning in the light of such considerations as the following. According to realism, the world is supposed to exist, as we know it, independently of this knowledge. Let us once, then, remove all percipient beings from it, and leave only unorganised and vegetable nature. Rock, tree, and brook are there, and the blue heaven ; sun, moon, and stars light this world, as before ; yet certainly in vain, for there is no eye to see it. Let us now in addition place in it a percipient being. Now that world presents itself again in his brain, and repeats itself within it precisely as it was formerly without it. Thus to the first world a second has been added, which, although


completely separated from it, resembles it to a nicety. And now the subjective world of this perception is precisely so constituted in subjective, known space as the objective world in objective, infinite space. But the subjective world has this advantage over the objective, the knowledge that that space, outside there, is infinite ; indeed it can also give beforehand most minutely and accurately the whole con stitution or necessary properties of all relations which are possible, though not yet actual, in that space, and does not require to examine them. It can tell just as much with regard to the course of time, and also with regard to the relation of cause and effect which governs the changes in that external world. I think all this, when closely con sidered, turns out absurd enough, and hence leads to the conviction that that absolute objective world outside the head, independent of it and prior to all knowledge, which at first we imagined ourselves to conceive, is really no other than the second, the world which is known sub jectively, the world of idea, as which alone we are actually able to conceive it. Thus of its own accord the assumption forces itself upon us, that the world, as we know it, exists also only for our knowledge, therefore in the idea alone, and not a second time outside of it. 1 In accordance, then, with this assumption, the thing in itself, i.e., that which exists independently of our knowledge and of every know ledge, is to be regarded as something completely different from the idea and all its attributes, thus from objectivity in general. What this is will be the subject of our second book. On the other hand, the controversy concerning the reality of the external world considered in 5 of the first

1 I specially recommend here the expression, but I must confess that

passage in Lichtenberg s " Miscel- it has never been easy for me com-

laneous Writings " (Gothingen, 1801, pletely to comprehend it. It always

vol. ii. p. 12) : " Euler says, in his seems to me as if the conception

letters upon various subjects in con- being were something derived from

nection with natural science (vol. ii. our thought, and thus, if there are

p. 228), that it would thunder and no longer any sentient and thinking

lighten just as well if there were no creatures, then there is nothing more

man present whom the lightning whatever." might strike. It is a very common


volume rests upon the assumption, which has just been criticised, of an objective and a subjective world both in space, and upon the impossibility which arises in con nection with this presupposition of a transition from, one to the other, a bridge between the two. Upon this con troversy I have still to add the following remarks.

The subjective and the objective do not constitute a con tinuous whole. That of which we are immediately con scious is bounded by the skin, or rat her by the extreme ends of the nerves which proceed from the cerebral sys tem. Beyond this lies a world of which we have no knowledge except through pictures in our head. Now the question is, whether and how far there is a world inde pendent of us which corresponds to these pictures. The relation between the two could only be brought about by means of the law of causality ; for this law alone leads from what is given to something quite different from it. But this law itself has first of all to prove its validity. Now it must either be of objective or of subjective origin ; but in either case it lies upon one or the other side, and therefore cannot supply the bridge between them. If, as Locke and Hume assume, it is a posteriori, thus drawn from experience, it is of objective, origin, and belongs then itself to the external world which is in question. There fore it cannot attest the reality of this world, for then, according to Locke s method, causality would be proved from experience, and the reality of experience from causa lity. If, on the contrary, it is given a priori, as Kant has more correctly taught us, then it is of subjective origin, and in that case it is clear that with it we remain always in the subjective sphere. For all that is actually given empiri cally in perception is the occurrence of a sensation in the organ of sense ; and the assumption that this, even in general, must have a cause rests upon a law which is rooted in the form of our knowledge, i.e., in the functions of our brain. The origin of this law is therefore just as subjective as that of the sensation itself. The cause of the


given sensation, which is assumed in consequence of this law, presents itself at once in perception as an object, which has space and time for the form of its manifesta tion. But these forms themselves again are entirely of subjective origin ; for they are the mode or method of our faculty of perception. That transition from the sensation to its cause which, as I have repeatedly pointed out, lies at the foundation of all sense-perception is certainly suf ficient to give us the empirical presence in space and time of an empirical object, and is therefore quite enough for the practical purposes of life ; but it is by no means sufficient to afford us any conclusion as to the existence and real nature, or rather as to the intelligible substratum, of the phenomena which in this way arise for us. Thus that on the occasion of certain sensations occurring in my organs of sense there arises in my head a perception of things which are extended in space, permanent in time, and causally efficient by no means justifies the assump tion that they also exist in themselves, i.e., that such things with these properties belonging absolutely to them selves exist independently and outside of my head. This is the true outcome of the Kantian philosophy. It coin cides with an earlier result of Locke s, which is just as true, but far more easily understood. For although, as Locke s doctrine permits, external things are absolutely assumed as the causes of sensations, yet there can be no resemblance between the sensation in which the effect con sists and the objective nature of the cause which occasions it. For the sensation, as organic function, is primarily determined by the highly artificial and complicated nature of our organs of sense. It is therefore merely excited by the external cause, but is then perfected en tirely in accordance with its own laws, and thus is com pletely subjective. Locke s philosophy was the criticism of the functions of sense ; Kant has given us the criticism of the functions of the brain. But to all this we have yet to add the Berkeleian result, which has been revised by me,


that every object, whatever its origin may be, is as object already conditioned by the subject, is in fact merely its idea. The aim of realism is indeed the object without subject ; but it is impossible even to conceive such an object distinctly.

From this whole inquiry it follows with certainty and distinctness that it is absolutely impossible to attain to the comprehension of the inner nature of things upon the path of mere knowledge and perception. For knowledge always comes to things from without, and therefore must for ever remain outside them. This end would only be reached if we could find ourselves in the inside of things, so that their inner nature would be known to us directly. Now, how far this is actually the case is considered in my second book. But so long as we are concerned, as in this first book, with objective comprehension, that is, with know ledge, the world is, and remains for us, a mere idea, for here there is no possible path by which we can cross over to it.

But, besides this, a firm grasp of the point of view of idealism is a necessary counterpoise to that of materialism. The controversy concerning the real and the ideal may also be regarded as a controversy concerning the existence of matter. For it is the reality or ideality of this that is ultimately in question. Does matter, as such, exist only in our idea, or does it also exist independently of it ? In the latter case it would be the thing in itself ; and who ever assumes a self-existent matter must also, consistently, be a materialist, i.e., he must make matter the principle of explanation of all things. Whoever, on the contrary, denies its existence as a thing in itself is eo ipso an idealist. Among the moderns only Locke has definitely and without ambiguity asserted the reality of matter ; and therefore his teaching led, in the hands of Condillac, to the sensualism and materialism of the French. Only Berkeley directly and without modifications denies matter. The complete antithesis is thus that of idealism and ma terialism, represented in its extremes by Berkeley and the


French materialists (Hollbach). Fichte is not to be men tioned here : he deserves no place among true philosophers ; among those elect of mankind who, with deep earnestness, seek not their own things but the truth, and therefore must not be confused with those who, under this pretence, have only their personal advancement in view. Fichte is the father of the sham philosophy, of the disingenuous method which, through ambiguity in the use of words, incompre hensible language, and sophistry, seeks to deceive, and tries, moreover, to make a deep impression by assuming an air of importance in a word, the philosophy which seeks to bamboozle and humbug those who desire to learn. After this method had been applied by Schelling, it reached its height, as every one knows, in Hegel, in whose hands it developed into pure charlatanism. But whoever even names this Fichte seriously along with Kant shows that he has not even a dim notion of what Kant is. On the other hand, materialism also has its warrant. It is just as true that the knower is a product of matter as that matter is merely the idea of the knower ; but it is also just as one-sided. For materialism is the philosophy of the subject that forgets to take account of itself. And, accordingly, as against the assertion that I am a mere modification of matter, this must be insisted upon, that all matter exists merely in my idea; and it is no less right. A knowledge, as yet obscure, of these relations seems to have been the origin of the saying of Plato, " v\ij a\T]0ivov tyevbos " (materiel mendacium verax).

Realism necessarily leads, as we have said, to material ism. For if empirical perception gives us things in them selves, as they exist independently of our knowledge, experience also gives us the order of things in themselves, i.e., the true and sole order of the world. But this path leads to the assumption that there is only one thing in itself, matter; of which all other things are modifications; for the course of nature is here the absolute and only order of the world. To escape from these consequences, while


realism remained in undisputed acceptance, spiritualism was set up, that is, the assumption of a second substance outside of and along with matter, an immaterial substance. This dualism and spiritualism, equally unsupported by experience and destitute of proof and comprehensibility, was denied by Spinoza, and was proved to be false by Kant, who dared to do so because at the same time he established idealism in its rights. For with realism ma terialism, as the counterpoise of which spiritualism had been devised, falls to the ground of its own accord, because then matter and the course of nature become mere pheno mena, which are conditioned by the intellect, as they have their existence only in its idea. Accordingly spiritualism is the delusive and false safeguard against materialism, while the real and true safeguard is idealism, which, by making the objective world dependent upon us, gives the needed counterpoise to the position of dependence upon the objective world, in which we are placed by the course of nature. The world from which I part at death is, in another aspect, only my idea. The centre of gravity of existence falls back into the subject. What is proved is not, as in spiritualism, that the knower is independent of matter, but that all matter is dependent on him. Cer tainly this is not so easy to comprehend or so convenient to handle as spiritualism, with its two substances ; but ^aXe-Tro. ra Ka\a.

In opposition to the subjective starting-point, " the world is my idea," there certainly stands provisionally with equal justification the objective starting-point, " the world is matter," or " matter alone is absolute " (since it alone is not subject to becoming and passing away), or " all that exists is matter." This is the starting-point of Democritus, Leucippus, and Epicurus. But, more closely considered, the departure from the subject retains a real advantage ; it has the start by one perfectly justified step. For con sciousness alone is the immediate: but we pass over this if we go at once to matter and make it our starting-point.



On the other hand, it would certainly be possible to con struct the world from matter and its properties if these were correctly, completely, and exhaustively known to us (which is far from being the case as yet). For all that has come to be has become actual through causes, which could operate and come together only by virtue of the fundamental forces of matter. But these must be perfectly capable of demonstration at least objectively, even if sub jectively we never attain to a knowledge of them. But such an explanation and construction of the world would not only have at its foundation the assumption of an exist ence in itself of matter (while in truth it is conditioned by the subject), but it would also be obliged to allow all the original qualities in this matter to pass current and remain absolutely inexplicable, thus as gualitates occultce. (Of. 26, 27 of the first volume.) For matter is only the vehicle of these forces, just as the law of causality is only the arranger of their manifestations. Therefore such an explanation of the world would always remain merely relative and conditioned, properly the work of a physical science, which at every step longed for a metapliysic. On the other hand, there is also something inadequate about the subjective starting-point and first principle, " the world is my idea," partly because it is one-sided, since the world is far more than that (the thing in itself, will), and indeed its existence as idea is to a certain extent only accidental to it ; but partly also because it merely expresses the fact that the object is conditioned by the subject, without at the same time saying that the subject, as such, is also con ditioned by the object. For the assertion, " the subject would still remain a knowing being if it had no object, i.e., if it had absolutely no idea," is just as false as the asser tion of the crude understanding, " the world, the object, would still exist, even if there were no subject." A con sciousness without an object is no consciousness. A think ing subject has conceptions for its object; a subject of sense perception has objects with the qualities correspond-


ing to its organisation. If we rob the subject of all special characteristics and forms of its knowledge, all the pro perties of the object vanish also, and nothing remains but matter without form and quality, which can just as little occur in experience as a subject without the forms of its knowledge, but which remains opposed to the naked sub ject as such, as its reflex, which can only disappear along with it, Although materialism pretends to postulate nothing more than this matter for instance, atoms yet it unconsciously adds to it not only the subject, but also space, time, and causality, which depend upon special pro perties of the subject.

The world as idea, the objective world, has thus, as it were, two poles ; the simple knowing subject without the forms of its knowledge, and crude matter without form and quality. Both are completely unknowable ; the sub ject because it is that which knows, matter because with out form and quality it cannot be perceived. Yet both are fundamental conditions of all empirical perception. Thus the knowing subject, merely as such, which is a presupposition of all experience, stands opposed as its pure counterpart to the crude, formless, and utterly dead (i.e., will-less) matter, which is given in no experience, but which all experience presupposes. This subject is not in time, for time is only the more definite form of all its ideas. The matter which stands over against it is, like it, eternal and imperishable, endures through all time, but is, properly speaking, not extended, for exten sion gives form, thus it has no spatial properties. Every thing else is involved in a constant process of coming into being and passing away, while these two repre sent the unmoved poles of the world as idea. The per manence of matter may therefore be regarded as the reflex of the timelessness of the pure subject, which is simply assumed as the condition of all objects. Both belong to phenomena, not to the thing in itself, but they are the framework of the phenomenon. Both are arrived


at only by abstraction, and are not given immediately, pure and for themselves.

The fundamental error of all systems is the failure to understand this truth. Intelligence and matter are corre lates, i.e., the one exists only for the other, both stand and fall together, the one is only the reflex of the other. In deed they are really one and the same thing regarded from two opposite points of view ; and this one thing, I am here anticipating, is the manifestation of the will, or the thing in itself. Consequently both are secondary, and therefore the origin of the world is not to be sought in either of the two. But because of their failure to understand this, all systems (with the exception perhaps of that of Spinoza) sought the origin of all things in one of these two. Some of them, on the one hand, suppose an intelligence, vovs, as the absolutely First and STj/j^ovpyo^, and accordingly in this allow an idea of things and of the world to precede their actual existence; consequently they distinguish the real world from the world of idea ; which is false. There fore matter now appears as that through which the two are distinguished, as the thing in itself. Hence arises the difficulty of procuring this matter, the v\r], so that when added to the mere idea of the world it may impart reality to it. That original intelligence must now either find it ready to hand, in which case it is just as much an absolute First as that intelligence itself, and we have then two absolute Firsts, the Sr)/j,ioupyos and the v\r) ; or the abso lute intelligence must create this matter out of nothing, an assumption which our understanding refuses to make, for it is only capable of comprehending changes in matter, and not that matter itself should come into being or pass away. This rests ultimately upon the fact that matter is essential, the correlate of the understanding. On the other hand, the systems opposed to these, which make the other of the two correlates, that is, matter, the absolute First, suppose a matter which would exist without being per ceived ; and it has been made sufficiently clear by all that


has been said above that this is a direct contradiction, for by the existence of matter we always mean simply its being perceived. But here they encounter the difficulty of bringing to this matter, which alone is their absolute First, the intelligence which is finally to experience it. I have shown this weak side of materialism in 7 of the first volume. For me, on the contrary, matter and intelligence are inseparable correlates, which exist only for each other, and therefore merely relatively. Matter is the idea of the intelligence ; the intelligence is that in whose idea alone matter exists. The two together con stitute the world as idea, which is just Kant s phenomenon, and consequently something secondary. What is primary is that which manifests itself, the thing in itself, which we shall afterwards discover is the will. This is in itself neither the perceiver nor the perceived, but is entirely different from the mode of its manifestation.

As a forcible conclusion of this important and difficult discussion I shall now personify these two abstractions, and present them in a dialogue after the fashion of Pra- bodha Tschandro Daya. It may also be compared with a similar dialogue between matter and form in the "Duodccim Principia Philosophies, " of Eaymund Lully, c. I and 2.

The Subject.

I am, and besides me there is nothing. For the world is my idea.


Presumptuous delusion ! I, I am, and besides me there is nothing, for the world is my fleeting form. Thou art a mere result of a part of this form and altogether acci dental.

The Subject.

What insane arrogance ! Neither thou nor thy form would exist without me ; ye are conditioned by me. Whosoever thinks me away, and believes he can still think


ye there, is involved in gross delusion, for your existence apart from my idea is a direct contradiction, a meaningless form of words. Ye are simply means ye are perceived by me. My idea is the sphere of your existence; therefore I am its first condition.


Fortunately the audacity of your assertion will soon be put to silence in reality and not by mere words. Yet a few moments and thou actually art no more. With all thy boasting thou hast sunk into nothing, vanished like a shadow, and shared the fate of all my transitory forms. But I, I remain, unscathed and undiminished, from age to age, through infinite time, and behold unshaken the play of mv changing form.

/ o o

The Subject.

This infinite time through which thou boastest that thou livest, like the infinite space which thou fillest, exists only in my idea. Indeed it is merely the form of my idea which I bear complete in myself, and in which thou exhibitest thyself, which receives thee, and through which thou first of all existest. But the annihilation with which thou threatenest me touches me not ; were it so, then wouldst thou also be annihilated. It merely affects the individual, which for a short time is my vehicle, and which, like everything else, is my idea.


And if I concede this, and go so far as to regard thy existence, which is yet inseparably linked to that of these fleeting individuals, as something absolute, it yet remains dependent upon mine. For thou art subject only so far as thou hast an object ; and this object I am. I am its kernel and content, that which is permanent in it, that which holds it together, and without which it would be as disconnected, as wavering, and unsubstantial as the dreams


and fancies of thy individuals, which have yet borrowed from me even the illusive content they possess.

The Subject.

Thou dost well to refrain from contesting my existence on the ground that it is linked to individuals ; for, as in separably as I am joined to them, thou art joined to thy sister, Form, and hast never appeared without her. No eye hath yet seen either thee or me naked and isolated ; for we are both mere abstractions. It is in reality one being that perceives itself and is perceived by itself, but whose real being cannot consist either in perceiving or in being perceived, since these are divided between us two.


We are, then, inseparably joined together as necessary parts of one whole, which includes us both and exists through us. Only a misunderstanding can oppose us two hostilely to each other, and hence draw the false conclu sion that the one contests the existence of the other, with which its own existence stands or falls.

This whole, which comprehends both, is the world as idea, or the world of phenomena. When this is taken away there remains only what is purely metaphysical, the thing in itself, which in the second book we shall recognise as the will

1 84



WITH all transcendental ideality the objective world re tains empirical reality ; the object is indeed not the thing in itself, but as an empirical object it is real. It is true that space is only in iny head ; but empirically my head is in space. The law of causality can certainly never enable us to get quit of idealism by building a bridge between things in themselves and our knowledge of them, and thus certifying the absolute reality of the world, which exhibits itself in consequence of its applica tion ; but this by no means does away with the causal relation of objects to each other, thus it does not abolish the causal relation which unquestionably exists between the body of each knowing person and all other material objects. But the law of causality binds together only phenomena, and does not lead beyond them. With that law we are and remain in the world of objects, i.e., the world of phenomena, or more properly the world of ideas. Yet the whole of such a world of experience is primarily conditioned by the knowledge of a subject in general as its necessary presupposition, and then by the special forms of our perception and apprehension, thus necessarily be longs to the merely phenomenal, and has no claim to pass for the world of things in themselves. Indeed the subject itself (so far as it is merely the knowing subject) belongs to the merely phenomenal, of which it constitutes the complementary half.

Without application of the law of causality, however, perception of an objective world could never be arrived at ;


for this perception is, as I have often explained, essentially matter of the intellect, and not merely of the senses. The senses afford us mere sensation, which is far from being perception. The part played by sensations of the senses in perception was distinguished by Locke under the name secondary qualities, which he rightly refused to ascribe to things in themselves. But Kant, carrying Locke s method further, distinguished also, and refused to ascribe to things in themselves what belongs to the working up of this material (the sensations) by the brain. The result was, that in this was included all that Locke had left to things in themselves as primary qualities extension, form, solidity, &c. so that with Kant the thing in itself was reduced to a completely unknown quantity = x. With Locke accordingly the thing in itself is certainly without colour, sound, smell, taste, neither warm nor cold, neither soft nor hard, neither smooth nor rough ; yet it has still extension and form, it is impene trable, at rest or in motion, and has mass and number. With Kant, on the other hand, it has laid aside all these latter qualities also, because they are only possible by means of time, space, and causality, and these spring from an intellect (brain), just as colours, tones, smells, &c., originate in the nerves of the organs of sense. The thing in itself has with Kant become spaceless, unextended, and incorporeal. Thus what the mere senses bring to the perception, in which the objective world exists, stands to what is supplied by the functions of the brain (space, time, causality) as the mass of the nerves of sense stand to the mass of the brain, after subtracting that part of the latter which is further applied to thinking proper, i.e., to abstract ideas, and is therefore not possessed by the brutes. Eor as the nerves of the organs of sense impart to the pheno menal objects colour, sound, taste, smell, temperature, &c., so the brain imparts to them extension, form, impenetra bility, the power of movement, &c., in short all that can only be presented in perception by means of time, space,


and causality. How small is the share of the senses in perception, compared with that of the intellect, is also shown by a comparison of the nerve apparatus for receiv ing impressions with that for working them up. The mass of the nerves of sensation of the whole of the organs of sense is very small compared with that of the brain, even in the case of the brutes, whose brain, since they do not, properly speaking, i.e., in the abstract, think, is merely used for effecting perception, and yet when this is com plete, thus in the case of mammals, has a very considerable mass, even after the cerebellum, whose function is the systematic guidance of movements, has been taken away.

That excellent book by Thomas Eeid, the " Inquiry into the Human Mind" (first edition, 1764; 6th edition, 1810), as a negative proof of the Kantian truths, affords us a very thorough conviction of the inadequacy of the senses to pro duce the objective perception of things, and also of the non- empirical origin of the perception of space and time. Eeid refutes Locke s doctrine that perception is a product of the senses, by a thorough and acute demonstration that the collective sensations of the senses do not bear the least re semblance to the world as known in perception, and espe cially that the five primary qualities of Locke (extension, form, solidity, movement, and number) absolutely could not be afforded us by any sensation of the senses. Accordingly he gives up the question as to the mode of origination and the source of perception as completely insoluble ; and although altogether unacquainted with Kant, he gives us, as it were, according to the regula falsi, a thorough proof of the intellectual nature of perception (really first explained by me as a consequence of the Kantian doctrine), and also of the a priori source, discovered by Kant, of its consti tuent elements, space, time, and causality, from which those primary qualities of Locke first proceed, but by means of which they are easily constructed. Thomas Eeid s book is very instructive and well worth reading ten times more so than all the philosophy together that has


been written since Kant. Another indirect proof of the same doctrine, though in the way of error, is afforded by the French sensational philosophers, who, since Condillac trod in the footsteps of Locke, have laboured to show once for all that the whole of our perception and thinking can be referred to mere sensations (penser cest sentir), which, after Locke s example, they call iddes simples, and through the mere coming together and comparison of which the whole objective world is supposed to build itself up in our heads. These gentlemen certainly have des ide es lien simples. It is amusing to see how, lacking alike the profundity of the German and the honesty of the English philosopher, they turn the poor material of sensa tion this way and that way, and try to increase its impor tance, in order to construct out of it the deeply significant phenomena of the world of perception and thought. But the man constructed by them would necessarily be an Anencephalus, a T6te de crapaud, with only organs of sense and without a brain. To take only a couple of the better attempts of this sort out of a multitude of others, I may mention as examples Condorcet at the beginning of hi* book, "Des Progress de V Esprit Humain" and Tourtual on Sight, in the second volume of the " Scriptores Ophthal- mologici Minores" edidit Justus Radius (1828).

The feeling of the insufficiency of a purely sensational- istic explanation of perception is in like manner shown in the assertion which was made shortly before the appear ance of the Kantian philosophy, that we not only have ideas of things called forth by sensation, but apprehend the things themselves directly, although they lie outside us which is certainly inconceivable. And this was not meant in some idealistic sense, but was said from the point of view of common realism. This assertion is well and pointedly put by the celebrated Euler in his " Letters to a German Princess," vol. ii. p. 68. He says : " I there fore believe that the sensations (of the senses) contain something more than philosophers imagine. They are not


merely empty perceptions of certain impressions made in the brain. They do not give the soul mere ideas of things, but actually place before it objects which exist outside it, although we cannot conceive how this really hap pens." This opinion is explained by the following facts. Although, as I have fully proved, perception is brought about by application of the law of causality, of which we are conscious a priori, yet in sight the act of the under standing, by means of which we pass from the effect to the cause, by no means appears distinctly in conscious ness ; and therefore the sensation does not separate itself clearly from the idea which is constructed out of it, as the raw material, by the understanding. Still less can a dis tinction between object and idea, which in general does not exist, appear in consciousness ; but we feel the things themselves quite directly, and indeed as lying outside us, although it is certain that what is immediate can only be the sensation, and this is confined to the sphere of the body enclosed by our skin. This can be explained from the fact that outside us is exclusively a spatial determination. But space itself is a form of our faculty of perception, i.e., a function of our brain. Therefore that externality to us to which we refer objects, on the occasion of sensations of sight, is itself really within our heads ; for that is its whole sphere of activity. Much as in the theatre we see the mountains, the woods, and the sea, but yet everything is inside the house. From this it becomes intelligible that we perceive things in the relation of externality, and yet in every respect immediately, but have not within us an idea of the things which lie outside us, different from these things. For things are in space, and consequently also external to us only in so far as we perceive them. There fore those things which to this extent we perceive directly, and not mere images of them, are themselves only our ideas, and as such exist only in our heads. Therefore we do not, as Euler says, directly perceive the things them selves which are external to us, but rather the things


which are perceived by us as external to us are only our ideas, and consequently are apprehended by us imme diately. The whole observation given above in Euler s words, and which is quite correct, affords a fresh proof of Kant s Transcendental ^Esthetic, and of my theory of per ception which is founded upon it, as also of idealism in general. The directness and unconsciousness referred to above, with which in perception we make the transition from the sensation to its cause, may be illustrated by an analogous procedure in the use of abstract ideas or think ing. When we read or hear we receive mere words, but we pass from these so immediately to. the conceptions de noted by them, that it is as if we received the conceptions directly ; for we are absolutely unconscious of the tran sition from the words to the conceptions. Therefore it sometimes happens that we do not know in what language it was that we read something yesterday which we now remember. Yet that such a transition always takes place becomes apparent if it is once omitted, that is, if in a fit of abstraction we read without thinking, and then become aware that we certainly have taken in all the words but no conceptions. Only when we pass from abstract con ceptions to pictures of the imagination do we become conscious of the transposition we have made.

Further, it is really only in perception in the narrowest sense, that is, in sight, that in empirical apprehension the transition from the sensation to its cause takes place quite unconsciously. In every other kind of sense perception, on the contrary, the transition takes place with more or less distinct consciousness; therefore, in the case of apprehension through the four coarser senses, its reality is capable of being established as an immediate fact. Thus in the dark we feel a thing for a long time on all sides until from the different effects upon our hands we are able to construct its definite form as their cause. Further, if something feels smooth we sometimes reflect whether we may not have fat or oil upon our hands; and


again, if something feels cold we ask ourselves whether it may not be that we have very warm hands. When we hear a sound we sometimes doubt whether it was really an affection of our sense of hearing from without or merely an inner affection of it ; then whether it sounded near and weak or far off and strong, then from what direction it came, and finally whether it was the voice of a man or of a brute, or the sound of an instrument ; thus we investi gate the cause of each effect we experience. In the case of smell and taste uncertainty as to the objective nature of the cause of the effect felt is of the commonest oc currence, so distinctly are the two separated here. The fact that in sight the transition from the effect to the cause occurs quite unconsciously, and hence the illusion arises that this kind of perception is perfectly direct, and consists simply in the sensation alone without any opera tion of the understanding this has its explanation partly in the great perfection of the organ of vision, and partly in the exclusively rectilineal action of light. On account of the latter circumstance the impression itself leads directly to the place of the cause, and since the eye is capable of perceiving with the greatest exactness and at a glance all the fine distinctions of light and shade, colour and outline, and also the data in accordance with which the understanding estimates distance, it thus happens that in the case of impressions of this sense the operation of the understanding takes place with such rapidity and certainty that we are just as little conscious of it as of spelling when we read. Hence arises the delusion that the sensation itself presents us directly with the objects. Yet it is just in sight that the operation of the under standing, consisting in the knowledge of the cause from the effect, is most significant. By means of it what is felt doubly, with two eyes, is perceived as single ; by means of it the impression which strikes the retina upside down, in consequence of the crossing of the rays in the pupils, is put right by following back the cause of this in the same


direction, or as we express ourselves, we see things upright although their image in the eye is reversed ; and finally by means of the operation of the understanding magni tude and distance are estimated by us in direct perception from five different data, which are very clearly and beau tifully described by Dr. Thomas Reid. I expounded all this, and also the proofs which irrefutably establish the intellectual nature of perception, as long ago as 1816, in my essay "On Sight and Colour" (second edition, 1854; third edition, 1870), and with important additions fifteen years later in the revised Latin version of it which is given under the title, " Theoria Colorum Physiologica Eademque Primaria," in the third volume of the " Script&res Oplithal- mologici Minores" published by Justus Eadius in 1830 ; yet most fully and thoroughly in the second (and third) edition of my essay " On the Principle of Sufficient Reason," 21. Therefore on this important subject I refer to these works, so as not to extend unduly the present exposition.

On the other hand, an observation which trenches on the province of aesthetics may find its place here. It follows from the proved intellectual nature of perception that the sight of beautiful objects for example, of a beautiful view is also a phenomenon of the brain. Its purity and completeness, therefore, depends not merely on the object, but also upon the quality of the brain, its form and size, the fineness of its texture, and the stimulation of its activity by the strength of the pulse of the arteries which supply it. Accordingly the same view appears in different heads, even when the eyes are equally acute, as different as, for example, the first and last impressions of a copper plate that has been much used. This is the explanation of the difference of capacity for enjoying natural beauty, and consequently also for reproducing it, i.e., for occasioning a similar phenomenon of the brain by means of an entirely different kind of cause, the arrange ment of colours on a canvas.

The apparent immediacy of perception, depending on


its entire intellectuality, by virtue of which, as Euler says, we apprehend the thing itself, and as external to us, finds an analogy in the way in which we feel the parts of our own bodies, especially when they suffer pain, which when we do feel them is generally the case. Just as we imagine that we perceive things where they are, while the perception really takes place in the brain, we believe that we feel the pain of a limb in the limb itself, while in reality it also is felt in the brain, to which it is con ducted by the nerve of the affected part. Therefore, only the affections of those parts whose nerves go to the brain are felt, and not those of the parts whose nerves belong to the sympathetic system, unless it be that an unusually strong affection of these parts penetrates by some round about way to the brain, where yet for the most part it only makes itself known as a dull sense of discomfort, and always without definite determination of its locality. Hence, also, it is that we do not feel injuries to a limb whose nerve-trunk has been severed or ligatured. And hence, finally, the man who has lost a limb still some times feels pain in it, because the nerves which go to the brain are still there. Thus, in the two phenomena here compared, what goes on in the brain is apprehended as outside of it ; in the case of perception, by means of the understanding, which extends its feelers into the outer world ; in the case of the feeling of our limbs, by means of the nerves.

( 193 )



IT is not the object of my writings to repeat what has been said by others, and therefore I only make here some special remarks of my own on the subject of the senses.

The senses are merely the channels through which the brain receives from without (in the form of sensations) the materials which it works up into ideas of perception. Those sensations which principally serve for the objective comprehension of the external world must in themselves be neither agreeable nor disagreeable. This really means that they must leave the will entirely unaffected. Other wise the sensation itself would attract our attention, and we would remain at the effect instead of passing to the cause, which is what is aimed at here. For it would bring with it that marked superiority, as regards our consideration, which the will always has over the mere idea, to which we only turn when the will is silent. Therefore colours and sounds are in themselves, and so long as their impression does not pass the normal degree, neither painful nor pleasurable sensations, but appear with the indifference that fits them to be the material of pure objective perception. This is as far the case as was possible in a body which is in itself through and through will; and just in this respect it is worthy of admiration. Physiologically it rests upon the fact that in the organs of the nobler senses, thus in sight and hear ing, the nerves which have to receive the specific outward impression are quite insusceptible to any sensation of pain, "VOL. n.


and know no other sensation than that which is specifi cally peculiar to them, and which serves the purpose of mere apprehension. Thus the retina, as also the optic nerve, is insensible to every injury; and this is also the case with the nerve of hearing. In both organs pain is only felt in their other parts, the surroundings of the nerve of sense which is peculiar to them, never in this nerve itself. In the case of the eye such pain is felt principally in the conjunctiva ; in the case of the ear, in the meatus auditorius. Even with the brain this is the case, for if it is cut into directly, thus from above, it has no feeling. Thus only on account of this indifference with regard to the will which is peculiar to them are the sensations of the eye capable of supplying the understand ing with such multifarious and finely distinguished data, out of which it constructs in our head the marvellous ob jective world, by the application of the law of causality upon the foundation of the pure perceptions of space and time. Just that freedom from affecting the will which is characteristic of sensations of colour enables them, when their energy is heightened by transparency, as in the glow of an evening sky, in painted glass, and the like, to raise us very easily into the state of pure objective will-less perception, which, as I have shown in my third book, is one of the chief constituent elements of the aesthetic im pression. Just this indifference with regard to the will fits sounds to supply the material for denoting the in finite multiplicity of the conceptions of the reason.

Outer sense, that is, receptivity for external impressions as pure data for the understanding, is divided into Jive senses, and these accommodate themselves to the four elements, i.e., the four states of aggregation, together with that of imponderability. Thus the sense for what is firm (earth) is touch ; for what is fluid (water), taste ; for what is in the form of vapour, i.e., volatile (vapour, exhalation), smell; for what is permanently elastic (air), hearing; for what is imponderable (fire, light), sight. The second im-


ponderable, heat, is not properly an object of the senses, but of general feeling, and therefore always affects the will directly, as agreeable or disagreeable. From this classification there also follows the relative dignity of the senses. Sight has the highest rank, because its sphere is the widest and its susceptibility the finest. This rests upon the fact that what affects it is an imponderable, that is, something which is scarcely corporeal, but is quasi spiritual. Hearing has the second place, corresponding to air. However, touch is a more thorough and well- informed sense. For while each of the other senses gives us only an entirely one-sided relation to the object, as its sound, or its relation to light, touch, which is closely bound up with general feeling and muscular power, sup plies the understanding with the data at once for the form, magnitude, hardness, softness, texture, firmness, tempera ture, and weight of bodies, and all this with the least possibility of illusion and deception, to which all the other senses are far more subject. The two lowest senses, smell and taste, are no longer free from a direct affection of the will, that is, they are always agreeably or disagree ably affected, and are therefore more subjective than objective.

Sensations of hearing are exclusively in time, and there fore the whole nature of music consists in degrees of time, upon which depends both the quality or pitch of tones, by means of vibrations, and also their quantity or duration, by means of time. The sensations of sight, on the other hand, are primarily and principally in space; but secon darily, by reason of their duration, they are also in time.

Sight is the sense of the understanding which perceives ; hearing is the sense of the reason which thinks and ap prehends. Words are only imperfectly represented by visible signs ; and therefore I doubt whether a deaf and dumb man, who can read, but has no idea of the sound of the words, works as quickly in thinking with the mere visible signs of conceptions as we do with the real, i.e.,


the audible words. If he cannot read, it is well known that he is almost like an irrational animal, while the man born blind is from the first a thoroughly rational being.

Sight is an active, hearing a passive sense. Therefore sounds affect our mind in a disturbing and hostile manner, and indeed they do so the more in proportion as the mind is active and developed ; they distract all thoughts and instantly destroy the power of thinking. On the other hand, there is no analogous disturbance through the eye, no direct effect of what is seen, as such, upon the activity of thought (for naturally we are not speaking here of the influence which the objects looked at have upon the will) ; but the most varied multitude of things before our eyes admits of entirely unhindered and quiet thought. Therefore the thinking mind lives at peace with the eye, but is always at war with the ear. This oppo sition of the two senses is also confirmed by the fact that if deaf and dumb persons are cured by galvanism they become deadly pale with terror at the first sounds they hear (Gilbert s " Annalen der PkysiJc," vol. x. p. 382), while blind persons, on the contrary, who have been operated upon, behold with ecstasy the first light, and unwillingly allow the bandages to be put over their eyes again. All that has been said, however, can be explained from the fact that hearing takes place by means of a mechanical vibration of the nerve of hearing which is at once transmitted to the brain, while seeing, on the other hand, is a real action of the retina which is merely stimu lated and called forth by light and its modifications ; as I have shown at length in my physiological theory of colours. But this whole opposition stands in direct con flict with that coloured-ether, drum-beating theory which is now everywhere unblushingly served up, and which seeks to degrade the eye s sensation of light to a mechanical vibration, such as primarily that of hearing actually is, while nothing can be more different than the still, gentle effect of light and the alarm-drum of hearing. If we add


to this the remarkable circumstance that although we hear with two ears, the sensibility of which is often very different, yet we never hear a sound double, as we often see things double with our two eyes, we are led to the conjecture that the sensation of hearing does not arise in the labyrinth or in the cochlea, but deep in the brain where the two nerves of hearing meet, and thus the im pression becomes simple. But this is where the pons Varolii encloses the medulla oblongata, thus at the ab solutely lethal spot, by the injury of which every animal is instantly killed, and from which the nerve of hearing has only a short course to the labyrinth, the seat of acoustic vibration. Now it is just because its source is here, in this dangerous place, in which also all movement of the limbs originates, that we start at a sudden noise ; which does not occur in the least degree when we sud denly see a light ; for example, a flash of lightning. The optic nerve, on the contrary, proceeds from its thalami much further forward (though perhaps its source lies behind them), and throughout its course is covered by the anterior lobes of the brain, although always separated from them till, having extended quite out of the brain, it is spread out in the retina, upon which, on stimulation by light, the sensation first arises, and where it is really localised. This is shown in my essay upon sight and colour. This origin of the auditory nerve explains, then, the great disturbance which the power of thinking suffers from sound, on account of which thinking men, and in general all people of much intellect, are without excep tion absolutely incapable of enduring any noise. For it disturbs the constant stream of their thoughts, interrupts and paralyses their thinking, just because the vibration of the auditory nerve extends so deep into the brain, the whole mass of which feels the oscillations set up through this nerve, and vibrates along with them, and because the brains of such persons are more easily moved than those of ordinary men. On the same readiness to be set in


motion, and capacity for transmission, which characterises their brains depends the fact that in the case of persons like these every thought calls forth so readily all those analogous or related to it whereby the similarities, ana logies, and relations of things in general come so quickly and easily into their minds ; that the same occasion which millions of ordinary minds have experienced before brings them to the thought, to the discovery, that other people are subsequently surprised they did not reach themselves, for they certainly can think afterwards, but they cannot think before. Thus the sun shone on all statues, but only the statue of Memnon gave forth a sound. For this reason Kant, Gcethe, and Jean Paul were highly sensitive to every noise, as their biographers bear wit ness. 1 Gcethe in his last years bought a house which had fallen into disrepair close to his own, simply in order that he might not have to endure the noise that would be made in repairing it. Thus it was in vain that in his youth he followed the drum in order to harden himself against noise. It is not a matter of custom. On the other hand, the truly stoical indifference to noise of ordinary minds is astonishing. No noise disturbs them in their thinking, reading, writing, or other occupations, while the finer mind is rendered quite incapable by it. But just that which makes them so insensible to noise of every kind makes them also insensible to the beautiful in plastic art, and to deep thought or fine expression in literary art; in short, to all that does not touch their personal interests. The following remark of Lichtenberg s applies to the paralysing effect which noise has upon highly intellectual persons : " It is always a good sign \vhen an artist can be hindered by trifles from exercising

his art. ~F used to stick his fingers into sulphur if

he wished to play the piano. . . . Such things do not

1 Lichtenberg says in his " Xach- " I am extremely sensitive to all

richtcn und Bcmerkungcn von und noise, but it entirely loses its dis-

iiber sich sclbst " ( Vermisckte Schrif- agreeable character as soon as it is

ten, Gottinyen, 1800, vol. i. p. 43) : associated with a rational purpose."


interfere with the average mind ; ... it acts like a coarse sieve" (Vermischte Schriften, vol. i. p. 398). I have long really held the opinion that the amount of noise which any one can bear undisturbed stands in inverse propor tion to his mental capacity, and therefore may be regarded as a pretty fair measure of it. Therefore, if I hear the dogs barking for hours together in the court of a house without being stopped, I know what to think of the intel lectual capacity of the inhabitants. The man who habitu ally slams the door of a room, instead of shutting it with his hand, or allows this to go on in his house, is not only ill-bred, but is also a coarse and dull-minded fellow. That in English " sensible " also means gifted with under standing is based upon accurate and fine observation. We shall only become quite civilised when the ears are no longer unprotected, and when it shall no longer be the right of everybody to sever the consciousness of each thinking being, in its course of a thousand steps, with whistling, howling, bellowing, hammering, whip-cracking, barking, &c. &c. The Sybarites banished all noisy trades without the town; the honourable sect of the Shakers in North America permit no unnecessary noise in their villages, and the Moravians have a similar rule. Some thing more is said upon this subject in the thirtieth chapter of the second volume of the " Parerga."

The effect of music upon the mind, so penetrating, so direct, so unfailing, may be explained from the passive nature of hearing which has been discussed; also the after effect which sometimes follows it, and which consists in a specially elevated frame of mind. The vibrations of the tones following in rationally combined numerical relations set the fibre of the brain itself in similar vibra tion. On the other hand, the active nature of sight, opposed as it is to the passive nature of hearing, makes it intelligible why there can be nothing analogous to music for the eye, and the piano of colours was an absurd mistake. Further, it is just on account of the active


nature of the sense of sight that it is remarkably acute in the case of Leasts that hunt, i.e., beasts of prey, while conversely the passive sense of hearing is specially acute in those beasts that are hunted, that flee, and are timid, so that it may give them timely warning of the pursuer that is rushing or creeping upon them.

Just as we have recognised in sight the sense of the understanding, and in hearing the sense of the reason, so we might call smell the sense of the memory, because it recalls to us more directly than any other the specific impression of an event or a scene even from the most distant past.

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FROM the fact that we are able spontaneously to assign and determine the laws of relations in space without having recourse to experience, Plato concludes (Meno, p. 353, Bip.) that all learning is mere recollection. Kant, on the other hand, concludes that space is subjectively conditioned, and merely a form of the faculty of know ledge. How far, in this regard, does Kaut stand above Plato!

Cogito, ergo sum, is an analytical judgment. Indeed Parrnenides held it to be an identical judgment : " TO <yap avro voeiv ean re KO.I eivat " (nam intelliyere et esse idem est, Clem. Alex. Strom., vi. 2, 23). As such, however, or indeed even as an analytical judgment, it cannot contain any special wisdom ; nor yet if, to go still deeper, we seek to deduce it as a conclusion from the major premise, non-entis nulla sunt prcedicata. But with this proposition what Descartes really wished to express was the great truth that immediate certainty belongs only to self- consciousness, to what is subjective. To what is objective, OTI the other hand, thus to everything else, only indirect certainty belongs ; for it is arrived at through self- consciousness ; and being thus merely at second hand, it is to be regarded as problematical. Upon this depends the value of this celebrated proposition. As its opposite we may set up, in the sense of the Kantian philosophy, cogito, ergo est, that is, exactly as I think certain relations iu things (the mathematical), they must always occur in


all possible experience ; this was an important, profound, and a late appergu, which appeared in the form of the problem as to the possibility of synthetic judgments a priori, and has actually opened up the way to a deeper know ledge. This problem is the watchword of the Kantian philosophy, as the former proposition is that of the Cartesian, and shows ef olwv et? ola.

Kant very fitly places his investigations concerning time and space at the head of all the rest. For to the speculative mind these questions present themselves before all others : what is time ? what is this that consists of mere movement, without anything that moves it? and what is space? this omnipresent nothing, out of which nothing that exists can escape without ceasing to be anything at all ?

That time and space depend on the subject, are the mode in which the process of objective apperception is brought about in the brain, has already a sufficient proof in the absolute impossibility of thinking away time and space, while we can very easily think away everything that is presented in them. The hand can leave go of everything except itself. However, I wish here to illus trate by a few examples and deductions the more exact proofs of this truth which are given by Kant, not for the purpose of refuting stupid objections, but for the use of those who may have to expound Kant s doctrine in future.

" A right-angled equilateral triangle " contains no logical contradiction ; for the predicates do not by any means cancel the subject, nor are they inconsistent with each other. It is only when their object is constructed in pure perception that the impossibility of their union in it appears. Now if on this account we were to regard this as a contradiction, then so would every physical impossibility, only discovered to be such after the lapse of centuries, be a contradiction; for example, the com position of a metal from its elements, or a mammal with


more or fewer than seven cervical vertebra, 1 or horns and upper incisors in the same animal. But only logical impossibility is a contradiction, not physical, and just as little mathemathical. Equilateral and rectangled do not contradict each other (they coexist in the square), nor does either of them contradict a triangle. Therefore the incompatibility of the above conceptions can never be known by mere thinking, but is only discovered by percep tion merely mental perception, however, which requires no experience, no real object. We should also refer here to the proposition of Giordano Bruno, which is also found in Aristotle : " An infinitely large body is necessarily im movable" a proposition which cannot rest either upon experience or upon the principle of contradiction, since it speaks of things which cannot occur in any experience, and the conceptions " infinitely large " and " movable " do not contradict each other ; but it is only pure perception that informs us that motion demands a space outside the body, while its infinite size leaves no space over. Suppose, now. it should be objected to the first mathematical example that it is only a question of how complete a conception of a triangle the person judging has : if the conception is quite complete it will also contain the impossibility of a triangle being rectangular and also equilateral. The answer to this is : assume that his conception is not so complete, yet without recourse to experience he can, by the mere construction of the triangle in his imagination, extend his conception of it and convince himself for ever of the impossibility of this combination of these con ceptions. This process, however, is a synthetic judgment a priori, that is, a judgment through which, independently of all experience, and yet with validity for all experience, we form and perfect our conceptions. For, in general, whether a given judgment is analytical or synthetical can only be determined in the particular case according as

1 That the three-toed sloth has yet Owen still states this, " Osteologie nine must be regarded as a mistake ; Comp." p. 405.


the conception of the subject in the mind of the person judging is more or less complete. The conception " cat " contains in the mind of a Cuvier a hundred times more than in that of his servant ; therefore the same judg ments about it will be synthetical for the latter, and only analytical for the former. But if we take the conceptions objectively, and now wish to decide whether a given judgment is analytical or synthetical, we must change the predicate into its contradictory opposite, and apply this to the subject without a copula. If this gives a contradictio in adjecto, then the judgment was analytical ; otherwise it was synthetical.

That Arithmetic rests on the pure intuition or perception of time is not so evident as that Geometry is based upon that of space. 1 It can be proved, however, in the following manner. All counting consists in the repeated affirmation of unity. Only for the purpose of always knowing how often we have already affirmed unity do we mark it each time with another word : these are the numerals. Now repeti tion is only possible through succession. But suc cession, that is, being after one another, depends directly upon the intuition or perception of time. It is a con ception which can only be understood by means of this ;

1 This, however, does not excuse the end to condemn without cere- a professor of philosophy who, sitting mony the fundamental teaching of in Kant s chair, expresses himself a great genius in a tone of peremptory thus : " That mathematics as such decision, just as if it were Hegelian contains arithmetic and geometry is foolery. We must not, however, fail correct. It is incorrect, however, to notice that these little people to conceive arithmetic as the science struggle to escape from the track of of time, really for no other reason great thinkers. They would there- than to give a pendant (sic) to fore have done better not to attack geometry as the science of space " Kant, but to content themselves (Rosenkranz in the " Deutschen with giving their public full details Museum," 1857, May 14, No. 20). about God, the soul, the actual free- This is the fruit of Hegelism. If dom of the will, and whatever be- the mind is once thoroughly de- longs to that sort of thing, and then bauched with its senseless jargon, to have indulged in a private luxury serious Kantian philosophy will no in their dark back-shop, the philo- longer enter it. The audacity to sephical journal ; there they may talk at random about what one does do whatever they like without con- not understand has been inherited straint, for no one sees it. from the master, and one comes in


and thus counting also is only possible by means of time. This dependence of all counting upon time is also be trayed by the fact that in all languages multiplication is expressed by " time," thus by a time-concept : sexies, ega/cis, sixfois, sex mal. But simple counting is already a multiplication by one, and for this reason in Pestalozzi s educational establishment the children are always made to multiply thus : " Two times two is four times one." Aristotle already recognised the close relationship of number and time, and expounded it in the fourteenth chapter of the fourth book of the " Physics." Time is for him " the number of motion " (" 6 xpovos api0/j,os eart K.W- Tjcreco?"). He very profoundly suggests the question whether time could be if the soul were not, and answers it in the negative. If arithmetic had not this pure intuition or perception of time at its foundation, it would be no science a priori, and therefore its propositions would not have infallible certainty.

Although time, like space, is the form of knowledge of the subject, yet, just like space, it presents itself as inde pendent of the subject and completely objective. Against our will, or without our knowledge, it goes fast or slow. We ask what o clock it is ; we investigate time, as if it were something quite objective. And what is this objec tive existence ? Not the progress of the stars, or of the clocks, which merely serve to measure the course of time itself, but it is something different from all things, and yet, like them, independent of our will and knowledge. It exists only in the heads of percipient beings, but the uniformity of its course and its independence of the will give it the authority of objectivity.

Time is primarily the form of inner sense. Anticipat ing the following book, I remark that the only object of inner sense is the individual will of the knowing subject. Time is therefore the form by means of which self-con sciousness becomes possible for the individual will, which originally and in itself is without knowledge. In it the


nature of the will, which in itself is simple and identical, appears drawn out into a course of life. But just on account of this original simplicity and identity of what thus exhibits itself, its character remains always precisely the same, and hence also the course of life itself retains throughout the same key-note, indeed its multifarious events and scenes are at bottom just like variations of one and the same theme.

The a priori nature of the law of causality has, by Eng lishmen and Frenchmen, sometimes not been seen at all, sometimes not rightly conceived of ; and therefore some of them still prosecute the earlier attempts to find for it an empirical origin. Maine de Biran places this in the experience that the act of will as cause is followed by the movement of the body as effect. But this fact itself is untrue. We certainly do not recognise the really imme diate act of will as something different from the action of the body, and the two as connected by the bond of causa lity ; but both are one and indivisible. Between them there is no succession ; they are simultaneous. They are one and the same thing, apprehended in a double manner. That which makes itself known to inner apprehension (self-con sciousness) as the real act of will exhibits itself at once in external perception, in which the body exists objectively as an action of the body. That physiologically the action of the nerve precedes that of the muscle is here imma terial, for it does not come within self-consciousness; and we are not speaking here of the relation between muscle and nerve, but of that between the act of will and the action of the body. Now this does not present itself as a causal relation. If these two presented themselves to us as cause and effect their connection would not be so incom prehensible to us as it actually is ; for what we under stand from its cause we understand as far as there is an understanding of things generally. On the other hand, the movement of our limbs by means of mere acts of will is indeed a miracle of such common occurrence that we


no longer observe it ; but if we once turn our attention to it we become keenly conscious of the incomprehensibility of the matter, just because in this we have something before us which we do not understand as the effect of a cause. This apprehension, then, could never lead us to the idea of causality, for that never appears in it at all. Maine de Biran himself recognises the perfect simultane- ousness of the act of will and the movement (Nouvelles Considerations des Rapports du Physique au Moral, p. 377> 37 8 )- I n England Thomas Eeid (On the First Principles of Contingent Truths, Essay IV. c. 5) already asserted that the knowledge of the causal relation has its ground in the nature of the faculty of knowledge it self. Quite recently Thomas Brown, in his very tediously composed book, " Inquiry into the Eelation of Cause and Effect," 4th edit, 1835, says much the same thing, that that knowledge springs from an innate, intuitive, and instinctive conviction ; thus he is at bottom upon the right path. Quite unpardonable, however, is the crass ignorance on account of which in this book of 476 pages, of which 130 are devoted to the refutation of Hume, absolutely no mention is made of Kant, who cleared up the question more than seventy years ago. If Latin had remained the exclusive language of science such a thing would not have occurred. In spite of Brown s exposition, which in the main is correct, a modification of the doctrine set up by Maine de Biran, of the empirical origin of the fundamental knowledge of the causal relation, has yet found acceptance in England ; for it is not without a certain degree of plausibility. It is this, that we abstract the law of causality from the perceived effect of our own body upon other bodies. This was already refuted by Hume. I, however, have shown that it is untenable in my work, " Ueber den Willen in dcr Natur" (p. 75 of the second edition, p. 82 of the third), from the fact that since we apprehend both our own and other bodies objectively in spatial perception, the knowledge of causality must


already be there, because it is a condition of such percep tion. The one genuine proof that we are conscious of the law of causalty before all experience lies in the neces sity of making a transition from the sensation, which is only empirically given, to its cause, in order that it may become perception of the external world. Therefore I have substituted this proof for the Kantian, the incorrect ness of which I have shown. A most full and thorough exposition of the whole of this important subject, which is only touched on here, the a priori nature of the law of causality and the intellectual nature of empirical percep tion, will be found in my essay on the principle of suffi cient reason, 21, to which I refer, in order to avoid the necessity of repeating here what is said there. I have also shown there the enormous difference between the mere sensation of the senses and the perception of an objective world, and discovered the wide gulf that lies between the two. The law of causality alone can bridge across this gulf, and it presupposes for its application the two other forms which are related to it, space and time. Only by means of these three combined is the objective idea attained to. Now whether the sensation from which we start to arrive at apprehension arises through the resistance which is suffered by our muscular exertion, or through the impression of light upon the retina, or of sound upon the nerves of the brain, &c. &c., is really a matter of indifference. The sensation always remains a mere datum for the understanding, which alone is capable of apprehending it as the effect of a cause different from itself, which the understanding now perceives as external, i.e., as something occupying and filling space, which is also a form inherent in the intellect prior to all experi ence. Without this intellectual operation, for which the forms must lie ready in us, the perception of an objective, external world could never arise from a mere sensation within our skin. How can it ever be supposed that the mere feeling of being hindered in intended motion, which


occurs also in lameness, could be sufficient for this ? We may add to this that before I attempt to affect external things they must necessarily have affected me as motives. But this almost presupposes the apprehension of the ex ternal world. According to the theory in question (as I have remarked in the place referred to above), a man born without arms and legs could never attain to the idea of causality, and consequently could never arrive at the apprehension of the external world. But that this is not the case is proved by a fact communicated in Froriep s Notizen, July 1838, No. 133 the detailed account, accompanied by a likeness, of an Esthonian girl, Eva Lauk, then fourteen years old, who was born entirely without arms or legs. The account concludes with these words : " According to the evidence of her mother, her mental development had been quite as quick as that of her brothers and sisters ; she attained just as soon as they did to a correct judgment of size and distance, yet without the assistance of hands. Dorpat, ist March 1838, Dr. A. Hueck."

Hume s doctrine also, that the conception of causality arises from the custom of seeing two states constantly following each other, finds a practical refutation in the oldest of all successions, that of day and night, which no one has ever held to be cause and effect of each other. And the same succession also refutes Kant s false asser tion that the objective reality of a succession is only known when we apprehend the two succeeding events as standing in the relation of cause and effect to each other. Indeed the converse of this doctrine of Kant s is true. We know which of the two connected events is the cause and which the effect, empirically, only in the succession. Again, on the other hand, the absurd assertion of several professors of philosophy in our own day that cause and effect are simultaneous can be refuted by the fact that in cases in which the succession cannot be perceived on account of its great rapidity, we yet assume it with



certainty a priori, and with it the lapse of a certain time. Thus, for example, we know that a certain time must elapse between the falling of the flint and the projection of the bullet, although we cannot perceive it, and that this time must further be divided between several events that occur in a strictly determined succession the fall ing of the flint, the striking of the spark, ignition, the spread of the fire, the explosion, and the projection of the bullet. No man ever perceived this succession of events ; but because we know which is the cause of the others, we thereby also know which must precede the others in time, and consequently also that during the course of the whole series a certain time must elapse, although it is so short that it escapes our empirical apprehension ; for no one will assert that the projection of the bullet is actually simultaneous with the falling of the flint. Thus not only the law of causality, but also its relation to time, and the necessity of the succession of cause and effect, is known to us a priori. If we know which of two events is the cause and which is the effect, we also know which precedes the other in time ; if, on the contrary, we do not know which is cause and which effect, but only know in general that they are causally connected, we seek to discover the suc cession empirically, and according to that we determine which is the cause and which the effect. The falseness of the assertion that cause and effect are simultaneous further appears from the following consideration. An unbroken chain of causes and effects fills the whole of time. (For if this chain were broken the world would stand still, or in order to set it in motion again an effect without a cause would have to appear.) Now if every effect were simul taneous with its cause, then every effect would be moved up into the time of its cause, and a chain of causes and effects containing as many links as before would fill no time at all, still less an infinite time, but would be all together in one moment. Thus, under the assumption that cause and effect are simultaneous, the course of the world


shrinks up into an affair of a moment. This proof is analogous to the proof that every sheet of paper must have a certain thickness, because otherwise the whole book would have none. To say when the cause ceases and the effect begins is in almost all cases difficult, and often impossible. For the changes (i.e., the succession of states) are continuous, like the time which they fill, and therefore also, like it, they are infinitely divisible. But their succession is as necessarily determined and as un mistakable as that of the moments of time itself, and each of them is called, w r ith reference to the one which precedes it, " effect," and with reference to the one which follows it, " cause."

Every change in the material world can only take place be cause another has immediately preceded it: this is the true and the whole content of the law of causality. But no concep tion has been more misused in philosophy than that of cause, by means of the favourite trick or blunder of conceiving it too widely, taking it too generally, through abstract think ing. Since Scholasticism, indeed properly since Plato and Aristotle, philosophy has been for the most part a systematic misuse of general conceptions. Such, for example, are sub stance, ground, cause, the good, perfection, necessity, and very many others. A tendency of the mind to work with such abstract and too widely comprehended conceptions has shown itself almost at all times. It may ultimately rest upon a certain indolence of the intellect, which finds it too difficult a task to be constantly controlling thought by perception. By degrees such unduly wide conceptions come to be used almost like algebraical symbols, and tossed about like them, and thus philosophy is reduced to a mere process of combination, a kind of reckoning which (like all calculations) employs and demands only the lower facul ties. Indeed there finally results from this a mere juggling with words, of which the most shocking example is afforded us by the mind-destroying Hegelism, in which it is carried to the extent of pure nonsense. But Scholasticism also


often degenerated into word-juggling. Nay, even the " Topi " of Aristotle very abstract principles, conceived with absolute generality, which one could apply to the most different kinds of subjects, and always bring into the field in arguing either pro or contra have also their origin in this misuse of general conceptions. We find innumer able examples of the way the Schoolmen worked with such abstractions in their writings, especially in those of Thomas Aquinas. But philosophy really pursued the path which was entered on by the Schoolmen down to the time of Locke and Kant, who at last bethought themselves as to the origin of conceptions. Indeed we find Kant himself, in his earlier years, still upon that path, in his " Proof of the Existence of God" (p. 191 of the first volume of Eosenkranz s edition), where the conceptions substance, ground, reality, are used in such a way as would never have been possible if he had gone back to the source of these conceptions and to their true content which is deter mined thereby. For then he would have found as the source and content of substance simply matter, of ground (if things of the real world are in question) simply cause, that is, the prior change which brings about the later change, &c. It is true that in this case such an investi gation would not have led to the intended result. But everywhere, as here, such unduly wide conceptions, under which, therefore, more was subsumed than their true con tent would have justified, there have arisen false principles, and from these false systems. Spinoza s whole method of demonstration rests upon such uninvestigated and too widely comprehended conceptions. Now here lies the great merit of Locke, who, in order to counteract all that dogmatic unreality, insisted upon the investigation of the origin of the conceptions, and thus led back to perception and experience. Bacon had worked in a similar frame of mind, yet more with reference to Physics than to Meta physics. Kant followed the path entered upon by Locke, but in a higher sense and much further, as has already been


mentioned above. To the men of mere show who succeeded in diverting the attention of the public from Kant to themselves the results obtained by Locke and Kant were inconvenient. But in such a case they know how to ignore both the dead and the living. Thus without hesitation they forsook the only right path which had at last been found by those wise men, and philosophised at random with all kinds of indiscriminately collected conceptions, unconcerned as to their origin and content, till at last the substance of the Hegelian philosophy, wise beyond measure, was that the conceptions had no origin at all, but were rather themselves the origin and source of things. But Kant has erred in this respect. He has too much neglected empirical perception for the sake of pure perception a point which I have fully discussed in my criticism of his philosophy. With me perception is through out the source of all knowledge. I early recognised the misleading and insidious nature of abstractions, and in 1813, in my essay on the principle of sufficient reason, I pointed out the difference of the relations which are thought under this conception. General conceptions must indeed be the material in which philosophy deposits and stores up its knowledge, but not the source from which it draws it ; the terminus ad quern, not a quo. It is not, as Kant defines it, a science drawn from conceptions, but a science in conceptions. Thus the conception of causality also, with which we are here concerned, has always been taken far too widely by philosophers for the furtherance of their dogmatic ends, and much was imported into it which does not belong to it at all. Hence arose propositions such as the following : " All that is has its cause " " the effect cannot contain more than the cause, thus nothing that was not also in the cause " " causa est ndbilior suo effectu" and many others just as unwarranted. The following subtilty of that insipid gossip Proclus affords an elaborate and specially lucid example of this. It occurs in his " Institutio Thcologica," 76 : " Hav ro airo aKivr^rov ycyvo-


ama?, a^era^Krjrov e^ei TIJV vTrapfyv irav Se TO CLTCO , fj,6ra(3\r)Tr)v ei jap a/avrjTOV e<JTi TcavTrj TO TTotovv, ov 8ia Kiwrjcreays, a\\ avrw T&&gt; eivai Trapayei TO SevTepov a<f> eavTov." (Quidquid db immobili causa manat, immutdbilem habet essentiam [substantiam"]. Quidquid vero a mobili causa manat, essentiam habet mutdbilem. Si enim illud, quod aliquid facit, est prorsus immobile, non per inotum, sed per ipsum Esse producit ipsum secundum ex se ipso.~) Excellent ! But just show me a cause which is not itself set in motion : it is simply impossible. But here, as in so many cases, abstraction has thought away all determinations down to that one which it is desired to make use of without regard to the fact that the latter cannot exist without the former. The only correct ex pression of the law of causality is this : Every change has its cause in another change which immediately precedes it. If something happens, i.e., if a new state of things appears, i.e., if something is changed, then something else must have changed immediately before, and something else again before this, and so on ad infinitum, for a first cause is as impossible to conceive as a beginning of time or a limit of space. More than this the law of causality does not assert. Thus its claims only arise in the case of changes. So long as nothing changes there can be no question of a cause. For there is no a priori ground for inferring from the existence of given things, i.e., states of matter, their previous non-existence, and from this again their coming into being, that is to say, there is no a priori ground for inferring a change. Therefore the mere exist ence of a thing does not justify us in inferring that it has a cause. Yet there may be a posteriori reasons, that is, reasons drawn from previous experience, for the assumption that the present state or condition did not always exist, but has only come into existence in con sequence of another state, and therefore by means of a change, the cause of which is then to be sought, and also the cause of this cause. Here then we are involved in


the infinite regressus to which the application of the law of causality always leads. We said above : " Things, i.e., states or conditions of matter" for change and causality have only to do with states or conditions. It is these states which we understand by form, in the wider sense ; and only the forms change, the matter is permanent. Thus it is only the form which is subject to the law of causality. But the form constitutes the thing, i.e., it is the ground of the difference of things ; while matter must be thought as the same in all. Therefore the School men said, "Forma dat esse rei;" more accurately this proposition would run : Forma dat rei essentiam, materia existentiam. Therefore the question as to the cause of a thing always concerns merely its form, i.e., its state or quality, and not its matter, and indeed only the former so far as we have grounds for assuming that it has not always existed, but has come into being by means of a change. The union of form and matter, or of essentia and existentia, gives the concrete, which is always particular ; thus, the thing. And it is the forms whose union with matter, i.e., whose appearance in matter by means of a change, are subject to the law of causality. By taking the conception too widely in the abstract the mistake slipped in of extending causality to the thing absolutely, that is, to its whole inner nature and existence, thus also to matter, and ultimately it was thought justifiable to ask for a cause of the world itself. This is the origin of the cosmological proof. This proof begins by inferring from the existence of the world its non-existence, which preceded its existence, and such an inference is quite unjustifiable ; it ends, however, with the most fearful inconsistency, for it does away altogether with the law of causality, from which alone it derives all its evidencing power, for it stops at a first cause, and will not go further ; thus ends, as it were, by committing parricide, as the bees kill the drones after they have served their end. All the talk about the absolute is referable to a shaniefast, and therefore disguised cosmological proof,


which, in the face of the " Critique of Pure Reason," has passed for philosophy in Germany for the last sixty years. What does the absolute mean ? Something that is, and of which (under pain of punishment) we dare not ask further whence and why it is. A precious rarity for professors of philosophy ! In the case, however, of the honestly ex pressed cosmological proof, through the assumption of a first cause, and therefore of a first beginning in a time which has absolutely no beginning, this beginning is always pushed further back by the question : Why not earlier ? And so far back indeed that one never gets down from it to the present, but is always marvelling that the present itself did not occur already millions of years ago. In general, then, the law of causality applies to all things in the world, but not to the world itself, for it is immanent in the world, not transcendent ; with it it comes into action, and with it it is abolished. This depends ultimately upon the fact that it belongs to the mere form of our understanding, like the whole of the objective world, which accordingly is merely phenomenal, and is con ditioned by the understanding. Thus the law of causality has full application, without any exception, to all things in the world, of course in respect of their form, to the variation of these forms, and thus to their changes. It is valid for the actions of men as for the impact of a stone, yet, as we have said always, merely with regard to events, to changes. But if we abstract from its origin in the understanding and try to look at it as purely objective, it will be found in ultimate analysis to depend upon the fact that every thing that acts does so by virtue of its original, and therefore eternal or timeless, power ; therefore its present effect would necessarily have occurred infinitely earlier, that is, before all conceivable time, but that it lacked the temporal condition. This temporal condition is the occa sion, i.e., the cause, on account of which alone the effect only takes place now, but now takes place necessarily ; the cause assigns it its place in time.


But in consequence of that unduly wide view in abstract thought of the conception cause, which was considered above, it has been confounded with the conception offeree. This is something completely different from the cause, but yet is that which imparts to every cause its causality, i.e., the capability of producing au effect. I have ex plained this fully and thoroughly in the second book of the first volume, also in " The Will in Nature," and finally also in the second edition of the essay on the prin ciple of sufficient reason, 20, p. 44 (third edition, p. 45). This confusion is to be found in its most aggravated form in Maine de Biran s book mentioned above, and this is dealt with more fully in the place last referred to ; but apart from this it is also very common ; for example, when people seek for the cause of any original force, such as gravitation. Kant himself (Uber den Einzig Moglichen Beweisgrund, vol. i. p. 211-215 of Eosenkranz s edition) calls the forces of nature "efficient causes," and says " gravity is a cause." Yet it is impossible to see to the bottom of his thought so long as force and cause are not distinctly recognised as completely different. But the use of abstract conceptions leads very easily to their con fusion if the consideration of their origin is set aside. The knowledge of causes and effects, always perceptive, which rests on the form of the understanding, is neglected in order to stick to the abstraction cause. In this way alone is the conception of causality, with all its simplicity, so very frequently wrongly apprehended. Therefore even in Aristotle (" Metaph.," iv. 2) we find causes divided into four classes which are utterly falsely, and indeed crudely conceived. Compare with it my classification of causes as set forth for the first time in my essay on sight and colour, chap. I , and touched upon briefly in the sixth para graph of the first volume of the present work, but ex pounded at full length in my prize essay on the freedom of the will, p. 30-33. Two things in nature remain un touched by that chain of causality which stretches into


infinity in both directions ; these are matter and the forces of nature. They are both conditions of causality, while everything else is conditioned by it. For the one (matter) is that in which the states and their changes appear ; the other (forces of nature) is that by virtue of which alone they can appear at all. Here, however, one must remem ber that in the second book, and later and more thoroughly in " The Will in Nature," the natural forces are shown to be identical with the will in us; but matter appears as the mere visibility of the will ; so that ultimately it also may in a certain sense be regarded as identical with the will.

On the other hand, not less true and correct is what is ex plained in 4 of the first book, and still better in the second edition of the essay on the principle of sufficient reason at the end of 21, p. 77 (third edition, p. 82), that matter is causality itself objectively comprehended, for its entire nature consists in acting in general, so that it itself is thus the activity (evepyeut = reality) of things generally, as it were the abstraction of all their different kinds of acting. Accordingly, since the essence, essentia, of matter consists in action in general, and the reality, existentia, of things consists in their materiality, which thus again is one with action in general, it may be asserted of matter that in it existentia and essentia unite and are one, for it has no other attribute than existence itself in general and inde pendent of all fuller definitions of it. On the other hand, all empirically given matter, thus all material or matter in the special sense (which our ignorant materialists at the present day confound with matter), has already entered the framework of the forms and manifests itself onlv

v */

through their qualities and accidents, because in experience every action is of quite a definite and special kind, and is never merely general. Therefore pure matter is an object of thought alone, not of perception, which led Plotinus (Enneas II., lib. iv., c. 8 & 9) and Giordano Bruno (Delia Causa, dial. 4) to make the paradoxical assertion that


matter has no extension, for extension is inseparable from the form, and that therefore it is incorporeal. Yet Aristotle had already taught that it is not a body although it is corporeal : "crcof^a /j,ev OVK av eirj, aco/nart/cr] Se" (Stob. Ed., lib. i., c. 12, 5). In reality we think under pure matter only action, in the abstract, quite independent of the kind of action, thus pure causality itself; and as such it is not an object but a condition of experience, just like space and time. This is the reason why in the accompanying table of our pure a priori knowledge matter is able to take the place of causality, and therefore appears along with space and time as the third pure form, and therefore as de pendent on our intellect.

This table contains all the fundamental truths which are rooted in our perceptive or intuitive knowledge a priori, expressed as first principles independent of each other. What is special, however, what forms the content of arithmetic and geometry, is not given here, nor yet what only results from the union and application of those formal principles of knowledge. This is the subject of the "Metaphysical First Principles of Natural Science" expounded by Kant, to which this table in some measure forms the propsedutic and introduction, and with which it therefore stands in direct connection. In this table I have primarily had in view the very remarkable parallelism of those a priori principles of knowledge which form the framework of all experience, but specially also the fact that, as I have explained in 4 of the first volume, matter (and also causality) is to be regarded as a combination, or if it is preferred, an amalgamation, of space and time. In agreement with this, we find that what geometry is for the pure perception or intuition of space, and arithmetic for that of time, Kant s plwronomy is for the pure perception or intuition of the two united. For matter is primarily that which is movable in space. The mathematical point cannot even be conceived as movable, as Aristotle has shown ("Physics," vi. 10). This philosopher also himself


provided the first example of such a science, for in the fifth and sixth books of his " Physics " he determined a priori the laws of rest and motion.

Now this table may be regarded at pleasure either as a collection of the eternal laws of the world, and therefore as the basis of our ontology, or as a chapter of the physio logy of the brain, according as one assumes the realistic or the idealistic point of view ; but the second is in the last instance right. On this point, indeed, we have already come to an understanding in the first chapter ; yet I wish further to illustrate it specially by an example. Aristotle s book "De Xenophane" &c., commences with these weighty words of Xenophanes : " A iSiov eivai tyrja-iv, ei TI ea-nv, enrep //,?; evBe-^erai yeveadai jjurj^ev etc fjujSevos" (Sternum esse, inquit, quicquid est, siquidem fieri non potest, ut ex nihilo quippiam existat.) Here, then, Xenophanes judges as to the origin of things, as regards its possibility, and of this origin he can have had no experience, even by analogy; nor indeed does he appeal to experience, but judges apodictically, and therefore a priori. How can he do this if as a stranger he looks from without into a world that exists purely objectively, that is, independently of his knowledge ? How can he, an ephemeral being hurrying past, to whom only a hasty glance into such a world is permitted, judge apodictically, a priori and without experience concerning that world, the possibility of its existence and origin ? The solution of this riddle is that the man has only to do with his own ideas, which as such are the work of his brain, and the constitution of which is merely the manner or mode in which alone the function of his brain can be fulfilled, i.e., the form of his perception. He thus judges only as to the pheno mena of his own brain, and declares what enters into its forms, time, space, and causality, and what does not. In this he is perfectly at home and speaks apodictically. In a like sense, then, the following table of the Prcedica- liilia a priori of time, space, and matter is to be taken :




Of Time.

Of Space.

Of Matter.

(i) There is only one

(i) There is only one

(i) There is only one Mat

Time, and all different

Space, and all different

ter, and all different mate

times are parts of it.

spaces are parts of it.

rials are different states of

matter ; as such it is called


(2) Different times

(2) Different spaces

(2) Different matters (ma

are not simultaneous

are not successive but

terials) are not so through

but successive.


substance but through acci


(3) Time cannot be

(3) Space cannot be

(3) Annihilation of matter

thought away, but

ihought away, but

is inconceivable, but anni

everything can be

everything can be

hilation of all its forms and

thought away from it.

thought away from it.

qualities is conceivable.

(4) Time has three

(4) Space has three

(4) Matter exists, i.e., acts

divisions, the past, the

dimensions height,

in all the dimensions of

present, and the future,

breadth, and length.

space and throughout the

which constitute two

whole length of time, and

directions and a centre

thus these two are united

of indifference.

and thereby filled. In this

consists the true nature of

matter : thus it is through

and through causality.

(5) Time is infinitely

(5) Space is infinitely

(5) Matter is infinitely di




(6) Time is homogene

(6) Space is homo

(6) Matter is homogeneous

ous and a Continuum,

geneous and a Continu

and a Continuum, i.e., it

i.e., no one of its parts

um, i.e., no one of its

does not consist of originally

is different from the

parts is different from

different (homoiomeria) or

rest, nor separated from

the rest, nor separated

originally separated parts

it by anything that is

from it by anything

(atoms) ; it is therefore not

not time.

that is not space.

composed of parts, which

would necessarily be sepa

rated by something that was

not matter.

(7) Time has no be

(7) Space has no lim

(7) Matter has no origin

ginning and no end, but

its, but all limits are

and no end, but all coming

all beginning and end

in it.

into being and passing away

is in it.

are in it.

(8) By reason of time

(8) By reason of space

(8) 15y reason of matter

we count.

we measure.

we weigh.

(9) Rhythm is only

(9) Symmetry is only

(9) Equilibrium is only in

in time.

in space.


(10) We know the

(10) We know the

(10) We know the laws of

laws of time a priori.

laws of space a priori.

the substance of all acci

dents a priori.



Of Time.

Of Space.

Of Matter.

(n) Time can be per

(n) Space is imme

(n) Matter can only be

ceived a priori, al

diately perceptible a

thought a priori.

though only in the


form of a line.

(12) Time has no per

(12) Space can never

(12) The accidents change;

manence, but passes

pass away, but endures

the substance remains.

away as soon as it is

through all time.


(13) Time never rests.

(13) Space is immov

(13) Matter is indifferent


to rest and motion ; i. e. , it

is originally disposed to

wards neither of the two.

(14) Everything that

(14) Everything that

(14) Everything material

exists in time has dura

exists in space has a

has the capacity for action.



(15) Time has no dura

(15) Space has no mo

(15) Matter is what is per

tion, but all duration

tion, but all motion is

manent in time and mov

is in it, and is the

in it, and it is the

able in space ; by the com

persistence of what is

change of position of

parison of what rests with

permanent in contrast

what is moved, in con

what is moved we measure

with its restless course.

trast with its unbroken



(16) All motion is

(16) All motion is

(16) All motion is only

only possible in time.

only possible in space.

possible to matter.

(17) Velocity is, in

(17) Velocity is, in

(17) The magnitude of the

equal spaces, in inverse

equal times, in direct

motion, the velocity being

proportion to the time.

proportion to the space.

equal, is in direct geometri

cal proportion to the matter


(18) Time is not meas

(18) Space is measur

(18) Matter as such (mass)

urable directly through

able directly through

is measurable, i.e., deter-

itself, but only indirect

itself, and indirectly

minable as regards its quan

ly through motion,

through motion, which

tity only indirectly, only

which is in space and

is in time and space

through the amount of the

time together : thus

together : hence, for

motion which it receives

the motion of the sun

example, an hour s

and imparts when it is re

and of the clock meas

journey, and the dis

pelled or attracted.

ure time.

tance of the fixed stars

expressed as the tra

velling of light for so

many years.

(19) Time is omni

(19) Space is eternal.

(19) Matter is absolute.

present. Every part

Every part of it exists

That is, it neither comes

of time is everywhere,


into being nor passes away,

i.e., in all space, at

and thus its quantity can


neither be increased nor




Of Time.

Of Space.

Of Matter.

(20) In time taken

(20) In space taken

(20, 21) Matter unites the

by itself everything

by itself everything

ceaseless flight of time with

would be in succession.

would be simultane

the rigid immobility of


space ; therefore it is the

(21) Time makes the

(21) Space makes the

permanent substance of the

change of accidents pos

permanence of sub

changing accidents. Causa


stance possible.

lity determines this change

for every place at every

time, and thereby combines

time and space, and consti

tutes the whole nature of


(22) Every part of

(22) No part of space

(22) For matter is both

time contains all parts

contains the same mat

permanent and impene

of matter.

ter as another.


(23) Time is the prin-

(23) Space is the prin-

(23) Individuals are ma

cipium individuationis.

cipiumindii iduationis.


(24) The now has no

(24) The point has no

(24) The atom has no




(25) Time in itself is

(25) Space in itself is

(25) Matter in itself is

empty and without pro

empty and without pro

without form and quality,



and likewise inert, i.e., in

different to rest or motion,

thus without properties.

(26) Every moment

(26) By the position

(26) Every change in mat

is conditioned by the

of every limit in space

ter can take place only on

preceding moment, and

with reference to any

account of another change

is only because the lat

other limit, its position

which preceded it ; and

ter has ceased to be.

with reference to every

therefore a first change,

(Principle of sufficient

possible limit is pre

and thus also a first state

reason of existence in

cisely determined.

of matter, is just as incon

time. See my essay on

(Principle of sufficient

ceivable as a beginning of

the principle of suffi

reason of existence in

time or a limit of space.

cient reason. )

space. )

(Principle of sufficient reason

of becoming.)

(27) Time makes ar

(27) Space makes geo

(27) Matter, as that which

ithmetic possible.

metry possible.

is movable in space, makes

phoronomy possible.

(28) The simple ele

(28) The simple ele

(28) The simple element

ment in arithmetic is

ment in geometry is

in phoronomy is the atom.


the point.



(i) To No. 4 of Matter.

The essence of matter is acting, it is acting itself, in the abstract, thus acting in general apart from all difference of the kind of action : it is through and through causality. On this account it is itself, as regards its existence, not subject to the law of causality, and thus has neither come into being nor passes away, for otherwise the law of causality would be applied to itself. Since now causality is known to us a priori, the conception of matter, as the indestructible basis of all that exists, can so far take its place in the knowledge we possess a priori, inasmuch as it is only the realisation of an a priori form of our knowledge. For as soon as we see anything that acts or is causally efficient it presents itself eo ipso as material, and con versely anything material presents itself as necessarily active or causally efficient. They are in fact interchangeable conceptions. Therefore the word "actual " is used as synonymous with "material ; " and also the Greek KCIT evepyeiav, in opposition to Kara Svvafuv, reveals the same source, for evepyeia signifies action in general ; so also with actu in opposition to po- tentia, and the English "actually " for " wirklich." What is called space- occupation, or impenetrability, and regarded as the essential predicate of body (i.e. of what is material), is merely that kind of action which belongs to all bodies without exception, the mechanical. It is this universality alone, by virtue of which it belongs to the conception of body, and follows a priori from this conception, and therefore cannot be thought away from it without doing away with the conception itself it is this, I say, that distinguishes it from any other kind of action, such as that of electricity or chemistry, or light or heat. Kant has very accurately analysed this space-occupation of the mechanical mode of activity into repulsive and attractive force, just as a given mechanical force is analysed into two others by means of the parallelo gram of forces. But this is really only the thoughtful analysis of the phe nomenon into its two constituent parts. The two forces in conjunction exhibit the body within its own limits, that is, in a definite volume, while the one alone would diffuse it into infinity, and the other alone would con tract it to a point. Notwithstanding this reciprocal balancing or neutralisa tion, the body still acts upon other bodies which contest its space with the first force, repelling them, and with the other force, in gravitation, attracting all bodies in general. So that the two forces are not extinguished in their product, as, for instance, two equal forces acting in different directions, or + E and E, or oxygen and hydrogen in water. That impenetrability and gravity really exactly coincide is shown by their empirical inseparableness, in that the one never appears without the other, although we can separate them in thought.

I must not, however, omit to mention that the doctrine of Kant referred to, which forms the fundamental thought of the second part of his "Meta physical First Principles of Natural Science," thus of the Dynamics, was distinctly and fully expounded before Kant by Priestley, in his excellent "Disquisitions on Matter and Spirit, i and 2, a book which appeared


in 1777, and the second edition in 1782, while Kant s work was published in 1786. Unconscious recollection may certainly be assumed in the case of subsidiary thoughts, flashes of wit, comparisons, &c., but not in the case of the principal and fundamental thought. Shall we then believe that Kant silently appropriated such important thoughts of another man? and this from a book which at that time was new? Or that this book was unknown to him, and that the same thoughts sprang up in two minds within a short time? The explanation, also, which Kant gives, in the "Metaphysical First Principles of Natural Science " (first edition, p. 88 ; Rosenkranz s edition, p. 384), of the real difference between fluids and solids, is in substance already to be found in Kaspar Freidr. "Wolffs "Theory of Generation," Berlin 1764, p. 132. But what are we to say if we find Kant s most important and brilliant doctrine, that of the ideality of space and the merely phenomenal existence of the corporeal world, already expressed by Maupertuis thirty years earlier ? This will be found more fully referred to in Frauenstiidt s letters on my philosophy, Letter 14. Maupertuis expresses this paradoxical doctrine so decidedly, and yet without adducing any proof of it, that one must suppose that he also took it from somewhere else. It is very desirable that the matter should be further investigated, and as this would demand tiresome and extensive researches, some German Academy might very well make the question the subject of a prize essay. Now in the same relation as that in which Kant here stands to Priestley, and perhaps also to Kaspar Wolff, and Maupertuis or his predecessor, Laplace stands to Kant. For the principal and fundamental thought of Laplace s admirable and certainly correct theory of the origin of the planetary system, which is set forth in his "Exposition du Systeme du Monde," liv. v. c. 2, was expressed by Kant nearly fifty years before, in 1755, in his " Naturgeschichte und Theorie des Himmels," and more fully in 1763 in his " Einzig moglichen Beiccisgrund des Daseyns Gottes" ch. 7. Moreover, in the later work he gives us to under stand that Lambert in his " Kosmologischcn Briefen," 1761, tacitly adopted that doctrine from him, and these letters at the same time also appeared in French (Lettres sur la Constitution de VUntiers. We are therefore obliged to assume that Laplace knew that Kantian doctrine. Certainly he expounds the matter more thoroughly, strikingly, and full} , and at the same time more simply than Kant, as is natural from his more profound astronomical knowledge ; yet in the main it is to be found clearly expressed in Kant, and on account of the importance of the matter, would alone have been sufficient to make his name immortal. It cannot but disturb us very much if we find minds of the first order under suspicion of dishonesty, which would be a scandal to those of the lowest order. For we feel that theft is even more inexcusable in a rich man than in a poor one. We dare not, however, be silent ; for here we are posterity, and must be just, as we hope that posterity will some day be just to us. Therefore, as a third example, I will add to these cases, that the fundamental thoughts of the "Metamorphosis of Plants," by Goethe, were already expressed by Kaspar Wolff in 1764 in his "Theory of Generation," p. 148, 229, 243, &c. Indeed, is it otherwise with the system of gravitation ? the discovery of which is on the Continent of Europe always ascribed to Newton, while in England the learned at least know very well that it belongs to Robert Hooke, who in the year 1666, in a "Communication to the Royal Society," expounds it quite distinctly, although only as an hypothesis and without proof. The VOL. II. P


principal passage of this communication is quoted in Dugalcl Stewart s Philosophy of the Human Mind, " and is probably taken from Robert Hooke s Posthumous Works. The history of the matter, and how Newton got into difficulty by it, is also to be found in the "Biographic UniverseUe," article Newton. Hooke s priority is treated as an established fact in a short history of astronomy, Quarterly Review, August 1828. Further details on this subject are to be found in my " Parerga," vol. ii., 86 (second edition, 88). The story of the fall of an apple is a fable as groundless as it is popular, and is quite without authority.

(2) To No. 1 8 of Matter.

The quantity of a motion (quantitas motus, already in Descartes) is the product of the mass into the velocity.

This law is the basis not only of the doctrine of impact in mechanics, but also of that of equilibrium in statics. From the force of impact which two bodies with the same velocity exert the relation of their masses to each other may be determined. Thus of two hammers striking with the same velocity, the one which has the greater mass will drive the nail deeper into the wall or the post deeper into the earth. For example, a hammer weigh ing six pounds with a velocity = 6 effects as much as a hammer weighing three pounds with a velocity = 12, for in both cases the quantity of motion or the momentum = 36. Of two balls rolling at the same pace, the one which has the greater mass will impel a third ball at rest to a greater distance than the ball of less mass can. For the mass of the first multiplied by the same velocity gives a greater quantity of motion, or a greater momen tum. The cannon carries further than the gun, because an equal velocity communicated to a much greater mass gives a much greater quantity of motion, which resists longer the retarding effect of gravity. For the same reason, the same arm will throw a lead bullet further than a stone one of equal magnitude, or a large stone further than quite a small one. And therefore also a case-shot does not carry so far as a ball-shot.

The same law lies at the foundation of the theory of the lever and of the balance. For here also the smaller mass, on the longer arm of the lever or beam of the balance, has a greater velocity in falling ; and multiplied by this it may be equal to, or indeed exceed, the quantity of motion or the momentum of the greater mass at the shorter arm of the lever. In the state of rest brought about by equilibrium this velocity exists merely in intention or virtually, potentid, not actu ; but it acts just as well as actu, which is very remarkable.

The following explanation will be more easily understood now that these truths have been called to mind.

The quantity of a given matter can only be estimated in general according to its force, and its force can only be known in its expression. Now when we are considering matter only as regards its quantity, not its quality, this expression can only be mechanical, i.e., it can only consist in motion which it imparts to other matter. For only in motion does the force of matter become, so to speak, alive ; hence the expression vis viva for the manifesta tion of force of matter in motion. Accordingly the only measure of the quantity of a given matter is the quantity of its motion, or its momentum. In this, however, if it is given, the quantity of matter still appears in cou-


junction and amalgamated with its other factor, velocity. Therefore if we waut to know the quantity of matter (the mass) this other factor must be

C 1

eliminated. Now the velocity is known directly ; for it is y. But the other factor, which remains when this is eliminated, can always be known only relatively in comparison with other masses, which again can only be known themselves by means of the quantity of their motion, or their momentum, thus in their combination with velocity. "We must therefore compare one quantity of motion with the other, and then subtract the velocity from both, in order to see how much each of them owed to its mass. This is done by weighing the masses against each other, in which that quantity of motion is compared which, in each of the two masses, calls forth the attractive power of the earth that acts upon both only in proportion to their quantity. Therefore there are two kinds of weighing. Either we impart to the two masses to be compared equal velocity, in order to find out which of the two now communicates motion to the other, thus itself has a greater quantity of motion, which, since the velocity is the same on both sides, is to be ascribed to the other factor of the quantity of motion or the momentum, thus to the mass (common balance). Or we weigh, by investigating how much more velocity the one mass must receive than the other has, in order to be equal to the latter in quantity of motion or momentum, and therefore allow no more motion to be communicated to itself by the other ; for then in propor tion as its velocity must exceed that of the other, its mass, i.e. , the quantity of its matter, is less than that of the other (steelyard). This estimation of masses by weighing depends upon the favourable circumstance that the moving force, in itself, acts upon both quite equally, and each of the two is in a position to communicate to the other directly its surplus quantity of motion or momentum, so that it becomes visible.

The substance of these doctrines has long ago been expressed by Newton and Kant, but through the connection and the clearness of this exposition I believe I have made it more intelligible, so that that insight is possible for all which I regarded as necessary for the justification of proposition No. 18.

( 228 ),