422 LEIBNITZ principle is now enunciated as the conservation of momentum, that of Leibnitz as the conservation of energy. Leibnitz further criticizes the Cartesian view that the mind can alter the direction of motion though it cannot imitate it, and contends that the quantity of "vis dircctiva," estimated between the same parts, is constant (p. 108) a position developed in his statical theorem for determining geome trically the resultant of any number of forces acting at a point. Like the monad, body, which is its analogue, has a passive and an active element. The former is the capacity of resistance, and includes impenetrability and inertia ; the latter is active force (pp. 250, 687). Bodies, too, like the monads, are self-contained activities, receiving no impulse from without it is only by an accommodation to ordinary language that we speak of them as doing so but moving themselves in harmony with each other (p. 250). The psychology of Leibnitz is chiefly developed in the Nouvcanx Essais sur T cntendemcnt humain, written in answer to Locke s famous Essay, and criticizing it chapter by chapter. In these essays he worked out a theory of the origin and development of knowledge in harmony with his metaphysical views, and thus without Locke s implied assumption of the mutual influence of soul and body. When one monad in an aggregate perceives the others so clearly that they are in comparison with it bare monads (monadcs nues), it is said to be the ruling monad of the aggregate, not because it actu ally does exert an influence over the rest, but because, being in close correspondence with them, and yet having so much clearer percep tion, it seems to do so (p. 683). This monad is called the entelechy or soul of the aggregate or body, and as such mirrors the aggregate in the first place and the universe through it (p. 710). Each soul or entelechy is surrounded by an infinite number of monads forming its body (p. 714); soul and body together make a living being, and, as their laws are in perfect harmony a harmony established between the whole realm of final causes and that of efficient causes (p. 714) we have the same result as if one influenced the other. This is further explained by Leibnitz in his well-known illustration of the different ways in which two clocks may keep exactly the same time. The machinery of the one may actually move that of the other, or whenever one moves the mechanician may make a similar alteration in the other, or they may have been so perfectly con structed at first as to continue to correspond at every instant with out any further influence (pp. 133, 134). The first way represents the common (Locke s) theory of mutual influence, the second the method of the occasionalists, the third that of pre-established har mony. Thus the body does not act on the soul in the production of cognition, nor the soul on the body in the production of motion. The body acts just as if it had no soul, the soul as if it had no body (p. 711). Instead, therefore, of all knowledge coming to us directly or indirectly through the bodily senses, it is all developed by the soul s own activity, and sensuous perception is itself but a confused kind of cognition. Not a certain select class of our idecis only (as Descartes held), but all our ideas, are innate, though only worked up into actual cognition in the development of knowledge (p. 212). To the aphorism made use of by Locke, " Nihil est in intellectu quod non prius fuerit in sensu," must be added the clause, "nisi intellectus ipse " (p. 223). The soul at birth is not comparable to a tabula rasa, but rather to an unworked block of marble, the hidden veins of which already determine the form it is to assume in the hands of the sculptor (p. 196). Nor, again, can the soul ever be withoiit perception ; for it has no other nature than that of a percipient active being (p. 246). Apparently dreamless sleep is to be accounted for by unconscious perception (p. 223); and it is by such insensible perceptions that Leibnitz explains his doctrine of pre-established harmony (p. 197). In the human soul perception is developed into thought, and there is thus an in finite though gradual difference between it and the mere monad (p. 464). As all knowledge is implicit in the soul, it follows that its perfection depends on the efficiency of the instrument by which it is developed. Hence the importance, in Leibnitz s system, of the logical principles and method the consideration of which oc cupied him at intervals throughout his whole career. There are two kinds of truths (1) truths of reasoning, and (2) truths of fact (pp. 83, 99, 707). The former rest on the principle of identity (or contradiction) or of possibility, in virtue of which that is false which contains a crmtradiction, and that true which is contradictory to the false. The latter rest on the principle of suffi cient reason or of reality (compossibilite), according to which no fact is true unless there be a sufficient reason why it should be so and not otherwise (agreeing thus with the principiuin mclioris or final cause). God alone, the purely active monad, has an a priori know ledge of the latter class of truths ; they have their source in the human mind only in so far as it mirrors the outer world, i.e., in its passivity, whereas the truths of reason have their source in our mind in itself or in its activity. Both kinds of truths fall into two classes, primitive and deriva tive. The primitive truths of fact are, as Descartes held, those of internal experience, and the derivative truths are inferred from them in accordance with the principle of sufficient reason, by their agree ment with our perception of the world as a whole. They are thus reached by probable arguments a department of logic which Leib nitz was thefirst to bring into prominence (pp. 84,164, 168,169, 343). The primitive truths of reasoning are identical (in later terminology, analytical) propositions, the derivative truths being deduced from them by the principle of contradiction. The part of his logic on which Leibnitz laid the greatest stress was the separation of these rational cognitions into their simplest elements for he held that the root-notions (cogitationes primse) would be found to be few in number (pp. 92, 93) and the designation of them by universal characters or symbols, 1 composite notions being denoted by the formulae formed by the union of several definite characters, and judgments by the relation of requipollence among these formulae, so as to reduce the syllogism to a calculus. This is the main idea of Leibnitz s "universal characteristic," never fully worked out by him, which he regarded as one of the greatest discoveries of the age. An incidental result of its adoption would be the intro duction of a universal symbolism of thought comparable to the symbolism of mathematics and intelligible in all languages (cf. p. 356). But the great revolution it would effect would chiefly consist in this, that truth and falsehood would be no longer matters of opinion but of correctness or error in calculation 2 (pp. 83, 84, 89, 93). The old Aristotelian analytic is not to be superseded ; but it is to be supplemented by this new method, for of itself it is but the ABC of logic. But the logic of Leibnitz is an art of discovery (p. 85) as well as of proof, and, as such, applies both to the sphere of reasoning and to that of fact. In the former it has by attention to render explicit what is otherwise only implicit, and by the intellect to introduce order into the a priori truths of reason, so that one may follow from another and they may constitute together a monde intdlcctud. To this art of orderly combination Leibnitz attached the greatest import ance, and to it one of his earliest writings was devoted. Similarly, in the sphere of experience, it is the business of the art of discovery to find out and classify the primitive facts or data, referring every other fact to them as its sufficient reason, so that new truths of ex perience may be brought to light. As the perception of the monad when clarified becomes thought, so the appetite of which all monads partake is raised to will, their spontaneity to freedom, in man (p. 669). The will is an effort or tendency to that which one finds good (p. 251), and is free only in the sense of being exempt from external control 3 (pp. 262, 513, 521), for it must always have a sufficient reason for its action determined by what seems good to it. The end determining the will is pleasure (p. 269), and pleasure is the sense of an increase of perfection (p. 670). A will guided by reason will sacrifice transitory and pursue constant pleasures or happiness, and in this weighing of pleasures consists true wisdom. Leibnitz, like Spinoza, says that freedom con sists in following reason, servitude in following the passions (p. 6C9), and that the passions proceed from confused perceptions (pp. 188, 269). In love one finds joy in the happiness of another ; and from love follow justice and law. " Our reason," says Leibnitz, 4 " illu mined by the spirit of God, reveals the law of nature," and with it positive law must not conflict. Natural law. rises from the strict command to avoid, offence, through the maxim of equity which gives to each his due, to that of probity or piety (honestc vivere),ic highest ethical perfection, which presupposes a belief in God, pro vidence and a future life. 5 Moral immortality not merely the simple continuity which belongs to every monad comes from God having provided that the changes of matter will not make man lose his individuality (pp. 126, 466). Leibnitz thus makes the existence of God a postulate of morality as well as necessary for the realization of the monads. It is in the Tlieodicee that his theology is worked out and his view of the uni verse as the best possible world defended. In it he contends that faith and reason are essentially harmonious (pp. 402, 479), and that nothing can be received as an article of faith which contradicts an eternal truth, though the ordinary physical order may be superseded by a higher. 6 The ordinary arguments for the being of God are retained by Leibnitz in a modified form (p. 375). Descartes s ontological proof is supplemented by the clause that God as the ens a sc must either exist or be impossible (pp. 80, 177, 708); in the cosmolpgical proof he passes from the infinite series of finite causes to their sufficient reason which contains all changes in the series necessarily in itself (pp. 147, 708) ; and he argues teleologically from tlie existence of harmony among the monads without any mutual influence to God as the author of this harmony (p. 430). i Different symbolic systems were proposed by Leibnitzat different peri Kvct, Leibnitzen s Loqik, 1857, p. 37. n ;, _ . i t x.-_i- T..:I ;*~ rt *,+;^;viof nri thn mnrlprn theory ot lotnc t 0^c;-a omnia. ed. Dutens. IV. iii. 282. 5 Ibid., IV. iii. 295. Cf. Bluntschli, Gesch. d. allg. StaatsrecJds u. PoHttt, 8 P. 480 ; cf. Werke, cd. Pcrtz, 2d sen, i. 158, 159.
