Diogenes (ix. 46-48) enumerates the titles of the treatises of Demokritus, as edited in the days of Tiberius by the rhetor Thrasyllus: who distributed them into tetralogies, as he also distributed the dialogues of Plato. It was probably the charm of style, common to Demokritus with Plato, which induced the rhetor thus to edit them both. In regard to scope and spirit of philosophy, the difference between the two was so marked, that Plato is said to have had a positive antipathy to the works of Demokritus, and a desire to burn them (Aristoxenus ap. Diog. Laert. ix. 40). It could hardly be from congeniality of doctrine that the same editor attached himself to both. It has been remarked that Plato never once names Demokritus, while Aristotle cites him very frequently, sometimes with marked praise.
Relation between the theory of Demokritus and that of Parmenides.
The theory of Leukippus and Demokritus (we have no means of distinguishing the two) appears to have grown out the Eleatic theory.[202] Parmenides the Eleate (as I have already stated) in distinguishing Ens, the self-existent, real, or absolute, on one side — from the phenomenal and relative on the other — conceived the former in such a way that its connection with the latter was dissolved. The real and absolute, according to him, was One, extended, enduring, continuous, unchangeable, immovable: the conception of Ens included these affirmations, and at the same time excluded peremptorily Non-Ens, or the contrary of Ens. Now the plural, unextended, transient, discontinuous, changeable, and moving, implied a mixture of Ens and Non-Ens, or a partial transition from one to the other. Hence (since Non-Ens was inadmissible) such plurality, &c., could not belong to the real or absolute (ultra-phenomenal), and could only be affirmed as phenomenal or relative. In the latter sense, Parmenides did affirm it, and even tried to explain it: he explained the phenomenal facts from phenomenal assumptions, apart from and independent of the absolute. While thus breaking down the bridge between the phenomenal on one side and the absolute on the other, he nevertheless recognised each in a sphere of its own.
[202] Simplikius, in Aristotel. Physic. fol. 7 A. Λεύκιππος … κοινωνήσας Παρμενίδῃ τῆς φιλοσοφίας, οὐ τὴν αὐτὴν ἐβάδισε Παρμενίδῃ καὶ Ξενοφάνει περὶ τῶν ὄντων δόξαν, ἀλλ’, ὡς δοκεῖ, τὴν ἐναντίαν. Aristotel. De Gener. et Corr. i. 8, p. 251, a. 31. Diogen. Laert. ix. 30.
Demokritean theory — Atoms — Plena and Vacua — Ens and Non-Ens.
This bridge the atomists undertook to re-establish. They admitted that Ens could not really change — that there could be no real generation, or destruction — no transformation of qualities — no transition of many into one, or of one into many. But they denied the unity and continuity and immobility of Ens: they affirmed that it was essentially discontinuous, plural, and moving. They distinguished the extended, which Parmenides had treated as an Unum continuum, into extension with body, and extension without body: into plenum and vacuum, matter and space. They conceived themselves to have thus found positive meanings both for Ens and Non-Ens. That which Parmenides called Non-Ens or nothing, was in their judgment the vacuum; not less self-existent than that which he called Something. They established their point by showing that Ens, thus interpreted, would become reconcilable to the phenomena of sense: which latter they assumed as their basis to start from. Assuming motion as a phenomenal fact, obvious and incontestable, they asserted that it could not even appear to be a fact, without supposing vacuum as well as body to be real: and the proof that both of them were real was, that only in this manner could sense and reason be reconciled. Farther, they proved the existence of a vacuum by appeal to direct physical observation, which showed that bodies were porous, compressible, and capable of receiving into themselves new matter in the way of nutrition. Instead of the Parmenidean Ens, one and continuous, we have a Demokritean Ens, essentially many and discontinuous: plena and vacua, spaces full and spaces empty, being infinitely intermingled.[203] There existed atoms innumerable, each one in itself essentially a plenum, admitting no vacant space within it, and therefore indivisible as well as indestructible: but each severed from the rest by surrounding vacant space. The atom could undergo no change: but by means of the empty space around, it could freely move. Each atom was too small to be visible: yet all atoms were not equally small; there were fundamental differences between them in figure and magnitude: and they had no other qualities except figure and magnitude. As no atom could be divided into two, so no two atoms could merge into one. Yet though two or more atoms could not so merge together as to lose their real separate individuality, they might nevertheless come into such close approximation as to appear one, and to act on our senses as a phenomenal combination manifesting itself by new sensible properties.[204]
[203] It is chiefly in the eighth chapter of the treatise De Gener. et Corr. (i. 8) that Aristotle traces the doctrine of Leukippus as having grown out of that of the Eleates. Λεύκιππος δ’ ἔχειν ᾠήθη λόγους, οἵτινες πρὸς τὴν αἴσθησιν ὁμολογούμενα λέγοντες οὐκ ἀναιρήσουσιν οὔτε γένεσιν οὔτε φθορὰν οὔτε κίνησιν καὶ τὸ πλῆθος τῶν ὄντων, &c.
Compare also Aristotel. De Cœlo, iii. 4, p. 303, a. 6; Metaphys. A. 4, p. 985, b. 5; Physic. iv. 6: λέγουσι δὲ (Demokritus, &c., in proving a vacuum) ἓν μὲν ὅτι ἡ κίνησις ἡ κατὰ τόπον οὐκ ἂν εἴη, οὐ γὰρ ἂν δοκεῖν εἶναι κίνησιν εἰ μὴ εἴη κενόν· τὸ γὰρ πλῆρες ἀδύνατον εἶναι δέξασθαί τι, &c.
Plutarch adv. Kolot. p. 1108. Οἷς οὐδ’ ὄναρ ἐντυχὼν ὁ Κολώτης, ἐσφάλη περὶ λέξιν τοῦ ἀνδρὸς (Demokritus) ἐν ᾖ διορίζεται, μὴ μᾶλλον τὸ δὲν, ἢ τὸ μηδὲν εἶναι· δὲν μὲν ὀνομάζων τὸ σῶμα μηδὲν δὲ τὸ κενόν, ὡς καὶ τούτου φύσιν τινὰ καὶ ὑπόστασιν ἰδίαν ἔχοντος.
The affirmation of Demokritus — That Nothing existed, just as much as Something — appears a paradox which we must probably understand as implying that he here adopted, for the sake of argument, the language of the Eleates, his opponents. They called the vacuum Nothing, but Demokritus did not so call it. If (said Demokritus) you call vacuum Nothing, then I say that Nothing exists as well as Something.