Philosophical Works of the Late James Frederick Ferrier/Lectures on Greek Philosophy (1888)/Atomic School
ATOMIC SCHOOL.
1. Leucippus and Democritus were the propounders of the Atomic theory of the universe. The Atomic philosophy is founded on the supposition that the ultimate elements of the universe are particles exceedingly minute and absolutely least. By absolutely least is meant small in the last degree—so small that the particle cannot be smaller. Such a degree of smallness is, of course, a fiction, for we cannot conceive anything arrested at a stage at which its quantity cannot be supposed to be diminished. The Atomic philosophers, however, supposed that such an arrestment did take place in nature. They supposed that all things were composed of particles, so little that they could not be less, particles which could not be severed by any force; and these particles they called atoms, using that word to denote their indivisible character.
2. The atom may be further described as that which entirely fills the space which it occupies. You will observe that any aggregate of atoms, any material thing which we behold, occupies considerably more space than it fills. This is proved by the consideration that everything admits of compression. All sensible matter, therefore, is porous; dense as some kinds of it may appear, the particles even of the most compact matter are never actually in contact, consequently all bodies occupy more space than they fill, or perhaps we should rather say, appear to fill more space than they actually do fill. All matter is interspersed with vacant cavities or interstices. The atom alone has no such interstices; it alone fills actually the same space in which it is.
3. The atom, then, besides being the absolutely least, is also the absolutely full, while the interval between atom and atom is the absolutely void, empty space. Empty space is thus the supplementing conception which the Atomic philosophers conjoin with their conception of the atom. What Being and not-Being were to Heraclitus, the full and the empty (τὸ πλῆρες καὶ τὸ κενόν), or atoms and the void, were to the Atomists. These (the full and the empty) were the principles of their system; and out of these they conceived that the constitution of the universe, and all the appearances which it presents to our senses, might be explained.
4. Another consideration to be kept particularly in view in studying this system is, that the atoms were not distinguished from each other by any differences of quality. In point of quality they were homogeneous, or of the same kind; their differences are quantitative merely, that is to say they differed from each other in size, weight, figure, arrangement, agility of motion, these being mere quantitative differences; but they did not differ from each other in being hot or cold, luminous or dark, sweet or bitter, wet or dry, for these are qualitative distinctions. Such distinctions were held to have no reality in rerum natura; all objective reality and objective difference were reduced to quantity alone.
5. The atoms were thus closely analogous to the pure Being of Parmenides and the Eleatics. They were of one uniform quality, if, indeed, quality could be attributed to them at all. The distinction between the two schools, the Eleatic and the Atomic, was that while no differences, either qualitative or quantitative, had places in the pure Being of the Eleatics, the Atomic philosophers represented their primordial constituents as differing, as has been said, in size, shape, arrangement, &c. In like manner the Atomic school differed from Empedocles, who had attributed differences of quality to his four elements, fire, air, earth, and water. Empedocles had thought that this postulate was necessary in order to account for the changing phenomena of the universe. The Atomists were of opinion that these changes might be accounted for without any such postulate.
6. The aim of the Atomic philosophers was to explain the greatest number of phenomena by means of the fewest possible principles. This striving after unity or simplicity is indeed the great aim or characteristic of all philosophy. It is what we have frequently described as the pursuit of the universal in all things; and in joining in this pursuit the Atomists made but common cause, and had the same object in view, with the rest of their brethren. What we have to consider more particularly in regard to them is, first, the effect which their principles had in simplifying the theory of the universe; and, secondly, the effect which their principles had in simplifying the theory of human perceptions and sensations. These are the two points in which, I think, the interest of the Atomic philosophy centres: first, the tendency of their doctrine to afford a simpler explanation of the phenomena of the universe; and, secondly, a simpler explanation of man's perceptions than any hitherto propounded. I do not say that their explanation is true or successful, but it has, at any rate, the merit of simplicity. Let us consider separately each of the two points adverted to.
7. First, Before the time of the Atomic philosophers things were supposed to have qualitative as well as quantitative differences. That things differed from each in quantity, in size, in shape, and weight, for example, was sufficiently obvious; and it was thought to be no less obvious that they differed from each other in quality; that fire, for example, had a different quality or qualities from water; that sugar differed in quality from salt; that light differed in quality from sound; that wood differed in quality from stone and from iron, and so on. All these qualitative differences the Atomic theory abolished, or tended to abolish. It sought to reduce them all to the simplicity of mere quantitative differences. The atoms were held to have no qualitative differences. They differed, as has been said, from each merely in shape, arrangement, and position (σχῆμα τάξις καὶ θέσις), perhaps also in magnitude and weight. And it was the different configuration and arrangements of these exceedingly minute particles which imparted to the different objects in the universe their apparently qualitative differences. The atoms of fire, for example, are the same as those which compose water, only their size, weight, shape, and arrangement are different, and hence arises what seems to be a qualitative difference in the objects which result from their combination. So of sugar, and salt, and flesh. Here the same elements are differently combined; and hence sugar and salt appear to differ in quality. So of light and sound. The ultimate particles of these two are the same; but their configuration and arrangement are different, and hence a qualitative difference seems to subsist between them. So of wood, and stone, and iron. In reality there are no qualitative differences among these things, but only differences arising from the shape, and number, and arrangement of the insensible atoms of which these things are composed,—in other words, mere qualitative differences. For example, if you ask, Why is water soft and flowing? the answer would be, that the minute atoms of which it consists are smooth and round, and do not fit into each other—like small wheels or globes, they roll over each other, hence its yielding and fluid nature. Why, again, is iron fixed and unyielding? The answer is, because its minute and insensible particles are not smooth and round, but are jagged and uneven—have, as it were, teeth by which they cling to each other, and, thus cohering, form a compact and solid body. But in both cases the atoms are in themselves of the same quality; they are merely different in shape, size, arrangement, and these are not qualitative but quantitative differences. In short, there are in reality no differences in the universe, except differences of quantity. All qualitative differences are unreal, and are merely apparent. So much, then, for the way in which the Atomic philosophy simplifies, or aims at simplifying, whether successfully or not, the theory of the universe, by abolishing quality, and by reducing all the diversities of natural agents to a difference of quantity merely.
8. The second point of interest in the Atomic philosophy is the new theory of sensation and perception which it involved. It had hitherto been supposed that there were certain qualities in objects corresponding to our sensations, and by which our sensations were induced. This was a matter on which probably no great attention had been bestowed; and therefore we cannot say very exactly what the previous doctrine in regard to sensation and perception may have been; but we are safe in affirming that it had been loosely assumed that there were, as I have said, certain qualities or agents corresponding to our sensations, and by which our sensations were induced. That, I think, we may say, was the general opinion, as it is indeed the vulgar, if not the philosophic, opinion to this day. When we feel the sensation of heat, we suppose there is some corresponding quality in the fire, or whatever the agent may be which induces it. When we see coloured objects we think that the colours are in the objects themselves, or, at any rate, that there is some quality in the object which causes our sensations of colour. When we have the sensation in our mouths of sweet or of bitter, we suppose that these different tastes are excited by different qualities in the objects. The Atomic theory corrected or modified this opinion, and this correction followed as a consequence of the Atomic doctrine in regard to the constitution of material things. If the atoms, the ultimate constituents of all things, are identical in point of quality, and differ only in size, shape, position, and arrangement, it follows that there can be nothing in real nature corresponding to what we call heat or cold, or sweet or bitter, or colour. These are merely sensations in us; not only are they mere sensations in us, there are, moreover, no qualities in things by which they are induced. How, then, are these various sensations induced? They are induced by the quantitative differences of the atoms. For instance, the atoms which occasion the sensation of heat, the atoms which occasion the sensation of smell, the atoms which occasion the sensation of taste, of touch, the atoms which occasion the sensation of sound, the atoms which occasion the sensation of colour—all these atoms are the same in themselves, only, in consequence of their different magnitudes, and shapes, and motions, they affect our sentient organism differently, and hence arises the variety in our sensations. The atoms which induce the sensation of heat are, we may suppose, exceedingly fine, sharp, and agile; the atoms which occasion our sensations of taste are perhaps less subtle and less sharp; and so in regard to the other atoms by which our other sensations are excited. Thus a mere quantitative difference in the atoms, their sharpness or smoothness, their subtlety or comparative grossness, their slowness or velocity, is held to be sufficient to explain all our varied sensations. And thus, too, a mere quantitative difference in the atoms will explain not only the different impressions which arise in our different senses, but also the different impressions which arise in the same sense. Thus the configuration of the atoms which induce the taste of bitterness, is different from the configuration of atoms which induce the sensation of sweetness; and thus the quality of syrup in itself is not different from the quality of vinegar, only the atoms of which each is composed are differently figured and arranged, and hence affect the palate differently. The same explanation would of course apply to the phenomena of the other senses. Different colours are seen because the atoms of light affect the retina differently, some of them impinging on it with greater force and rapidity than others. Such is the manner in which the Atomic philosophers explained the phenomena of sensation and perception. To things themselves they allowed mere quantitative differences, such differences as consist in number, size, figure, motion, weight, and arrangement. These are the only differences which truly exist, which are in rerum natura; because these are the only differences which exist in the atoms of which things are composed. All qualitative differences, such as heat and cold, sweet and bitter, colour and sound—all these they placed in the sentient subject, and regarded as mere affections of the mind or nervous system. Thus the world had reality only in so far as quantity was concerned. In regard to quality, it had no reality out of or beyond the mind of man; and thus, while quantitative difference was real and objective, qualitative difference was only apparent and subjective.
9. It is obvious that this theory of sensation bears a close resemblance to the doctrine frequently propounded in more recent times in regard to the primary and secondary qualities of matter. The doctrine, as you know, is this, that the primary qualities are extension, figure, and solidity; that these exist objectively in the things themselves, and that we have a direct perception of them as they thus exist; while again the secondary qualities, such as heat and cold, colours and sounds, tastes and smell, are subjective affections existing merely in us. These are not properly the qualities of matter, but are rather the names of our sensations. The difference, however, between this doctrine and that of the Atomists consists in this circumstance, that while the modern propounders of the doctrine have held that there were certain occult qualities in matter corresponding to our sensations of heat, colour, taste, smell, and so forth—occult qualities by which these sensations are induced—the Atomists had recourse to no such hypothesis. They conceived that the nature of the atoms, which has been already explained as consisting in differences of shape and arrangement—they conceived that this was quite sufficient of itself to account for the variety of our sensations, and accordingly the hypothesis of occult qualities really existing in material things, and inducing our sensations, formed no part of their system. Our sensations were explained on mechanical and quantitative grounds as resulting from the different shapes and degrees of solidity in the atoms by which our organs of sense were affected. The Atomic theory of sensation and perception was thus considerably simpler than the doctrine propounded by Reid and others in regard to the primary and secondary qualities of matter; and it certainly was quite as philosophical.
10. I conclude this account of the Atomic doctrine by remarking that, even in this system, we may observe that tendency which I have said is the characteristic more or less of all speculative philosophy, the tendency, namely, to aim at truth for all rather than at truth for some intelligence. This tendency is not so conspicuous in the Atomic scheme as it is in some other systems; but even here it is unmistakably manifested. What the Atomists called the full and the empty, atoms and the void, which was their expression for what are nowadays called the primary qualities of matter—these are more universal in their character than such qualities as heat and cold, sweet and bitter, luminous and dark; these latter qualities could not be understood except by intelligences endowed with senses like ours; but the full and the empty, in other words, atoms and the void, would, in all probability, be intelligible to pure intellect, and certainly approach more nearly to the character of truths for all intellect than do any of those truths which are known to us as the secondary qualities of matter.