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previous: Chapter 9 This webpage reproduces a chapter of A History of Philosophy by Frederick Copleston, S. J. as reprinted by Image Books — Doubleday New York • London • Toronto • Sydney • Auckland 1993 The text, and illustrations except as noted, are in the public domain. next: Chapter 11

Part I: Pre‑Socratic Philosophy

 p72  Chapter X
The Atomists

The founder of the Atomist School was Leucippus of Miletus. It has been maintained that Leucippus never existed,​1 but Aristotle and Theophrastus make him to be the founder of the Atomist philosophy, and we can hardly suppose that they were mistaken. It is not possible to fix his dates, but Theophrastus declares that Leucippus had been a member of the School of Parmenides, and we read in Diogenes' Life of Leucippus that he was a disciple of Zeno (οὗτος ἤκουσε Ζήνωνος). It appears that the Great Diakosmos, subsequently incorporated in the works of Democritus of Abdera, was really the work of Leucippus, and no doubt Burnet is quite right when he compares the Democritean corpus with the Hippocratean, and remarks that in neither case can we distinguish the authors of the various component treatises.​2 The whole corpus is the work of a School, and it is most unlikely that we shall ever be in a position to assign each work to its respective author. In treating of the Atomist philosophy, therefore, we cannot pretend to distinguish between what is due to Leucippus and what is due to Democritus. But since Democritus is of considerably later date and cannot with historical accuracy be classed among the Pre‑Socratics, we will leave to a later chapter his doctrine of sense-perception, by which he attempted to answer Protagoras, and his theory of human conduct. Some historians of philosophy, indeed, treat of Democritus' views on these points when dealing with the Atomist philosophy in the section devoted to the Pre‑Socratics, but in view of the undoubtedly later date of Democritus, it seems preferable to follow Burnet in this matter.

The Atomist philosophy is really the logical development of the philosophy of Empedocles. The latter had tried to reconcile the Parmenidean principle of the denial of the passage of being into not‑being or vice versa, with the evident fact of change by postulating four elements which, mixed together in various proportions, form the objects of our experience. He did not, however, really work out his doctrine of particles, nor did he  p73 carry the quantitative explanation of qualitative differences to its logical conclusion. The philosophy of Empedocles formed a transitional stage to the explanation of all qualitative differences by a mechanical juxtaposition of material particles in various patterns. Moreover, Empedocles's forces — Love and Strife — were metaphorical powers, which would have to be eliminated in a thorough-going mechanical philosophy. The final step to complete mechanism was attempted by the Atomists.

According to Leucippus and Democritus there are an infinite number of indivisible units, which are called atoms. These are imperceptible, since they are too small to be perceived by the senses. The atoms differ in size and shape, but have no quality save that of solidity or impenetrability. Infinite in number, they move in the void. (Parmenides had denied the reality of space. The Pythagoreans had admitted a void to keep their units apart, but they identified it with the atmospheric air, which Empedocles showed to be corporeal. Leucippus, however, affirmed at the same time the non‑reality of space and its existence, meaning by non‑reality, non‑corporeity. This position is expressed by saying that "what is not" is just as much real as "what is." Space, then, or the void, is not corporeal, but it is as real as body.) The later Epicureans held that the atoms all move downwards in the void through the force of weight, probably influenced by Aristotle's idea of absolute weight and lightness. (Aristotle says that none of his predecessors had held this notion.) Now Aëtius expressly says that while Democritus ascribed size and shape to the atoms, he did not ascribe to them weight, but that Epicurus added weight in order to account for the movement of the atoms.​3 Cicero relates the same, and also declares that according to Democritus, there was no "top" or "bottom" or "middle" in the void.​4 If this is what Democritus held, then he was of course quite right, for there is no absolute up or down, but how in this case did he conceive the motion of the atoms? In the De Anima​5 Aristotle attributes to Democritus a comparison between the motions of the atoms of the soul and the motes in a sunbeam, which dart hither and thither in all directions, even when there is no wind. It may be that this was also the Democritean view of the original motion of the atoms.

However, in whatever way the atoms originally moved in the  p74 void, at some point of time collisions between atoms occurred, those of irregular shape becoming entangled with one another and forming groups of atoms. In this way the vortex (Anaxagoras) is set up, and a world is in process of formation. Whereas Anaxagoras thought that the larger bodies would be driven farthest from the centre, Leucippus said the opposite, believing, wrongly, that in an eddy of wind or water the larger bodies tend towards the centre. Another effect of the movement in the void is that atoms which are alike in size and shape are brought together as a sieve brings together the grains of millet, wheat and barley, or the waves of the sea heap up together long stones with long and round with round. In this way are formed the four "elements" — fire, air, earth and water. Thus innumerable worlds arise from the collisions among the infinite atoms moving in the void.

It is at once noticeable that neither Empedocles' forces, Love and Strife, nor the Nous of Anaxagoras appear in the Atomist philosophy: Leucippus evidently did not consider any moving force to be a necessary hypothesis. In the beginning existed atoms in the void, and that was all: from that beginning arose the world of our experience, and no external Power or moving Force is assumed as a necessary cause for the primal motion. Apparently the early cosmologists did not think of motion as requiring an explanation, and in the Atomist philosophy the eternal movement of the atoms is regarded as self-sufficient. Leucippus speaks of everything happening ἐκ λόγου καὶ ὑπ’ ἀνάγκης​6 and this might at first sight appear inconsistent with his doctrine of the unexplained original movement of the atoms and of the collisions of the atoms. The latter, however, occur necessarily owing to the configuration of the atoms and their irregular movements, while the former, as a self-sufficient fact, did not require further explanation. To us, indeed, it may well seem strange to deny chance and yet to posit an eternal unexplained motion — Aristotle blames the Atomists for not explaining the source of motion and the kind of motion​7 — but we ought not to conclude that Leucippus meant to ascribe the motion of the atoms to chance: to him the eternal motion and the continuation of motion required no explanation. In our opinion, the mind boggles at such a theory and cannot rest content with Leucippus' ultimate; but it is an interesting  p75 historical fact, that he himself was content with this ultimate and sought no "First Unmoved Mover."

It is to be noted that the atoms of Leucippus and Democritus are the Pythagorean monads endowed with the properties of Parmenidean being — for each is as the Parmenidean One. And inasmuch as the elements arise from the various arrangements and positions of the atoms, they may be likened to the Pythagorean "numbers," if the latter are to be regarded as patterns or "figurate numbers." This can be the only sense to be attached to Aristotle's dictum that "Leucippus and Democritus virtually make all things number too and produce them from numbers."8

In his detailed scheme of the world, Leucippus was somewhat reactionary, rejecting the Pythagorean view of the spherical character of the earth and returning, like Anaxagoras, to the view of Anaximenes, that the earth is like a tambourine floating in the air. But, though the details of the Atomist cosmology do not indicate any new advance, Leucippus and Democritus are noteworthy for having carried previous tendencies to their logical conclusion, producing a purely mechanical account and explanation of reality. The attempt to give a complete explanation of the world in terms of mechanical materialism has, as we all know, reappeared in a much more thorough form in the modern era under the influence of physical science, but the brilliant hypothesis of Leucippus and Democritus was by no means the last word in Greek philosophy: subsequent Greek philosophers were to see that the richness of the world cannot in all its spheres be reduced to the mechanical interplay of atoms.

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The Author's Notes:

1 Epicurus, for instance, denied his existence, but it has been suggested that this denial was due to Epicurus' determination to claim originality.

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2 E. G. P., p331.

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3 Aët. I.3.18 and 12.6 (D> 68 A 47)

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4 De Fato, 20, 46 and De Fin., I.6.17 (D. 68 A 47 and 56).

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5 De An., Α, 2, 403b28 ff.

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6 Frag. 2 (Aët., I.25.4).

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7 Phys., Θ I.252a32; De Caelo, Γ 2, 300b8; Metaph., Α, 4, 985b19‑20.

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8 De Caelo, Γ 4, 303a8.

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