All these theories were found in circulation by Sokrates, Zeno, Plato, and the dialecticians. Importance of the scrutiny of negative Dialectic.
In studying the writings of Plato and Aristotle, we must recollect that they found all these theories pre-existent or contemporaneous. We are not to imagine that they were the first who turned an enquiring eye on Nature. So far is this from being the case that Aristotle is, as it were, oppressed both by the multitude and by the discordance of his predecessors, whom he cites, with a sort of indulgent consciousness of superiority, as “the ancients” (οἱ ἀρχαῖοι).[9] The dialectic activity, inaugurated by Sokrates and Zeno, lowered the estimation of these cosmical theories in more ways than one: first, by the new topics of man and society, which Sokrates put in the foreground for discussion, and treated as the only topics worthy of discussion: next, by the great acuteness which each of them displayed in the employment of the negative weapons, and in bringing to view the weak part of an opponent’s case. When we look at the number of these early theories, and the great need which all of them had to be sifted and scrutinised, we shall recognise the value of negative procedure under such circumstances, whether the negationist had or had not any better affirmative theory of his own. Sokrates, moreover, not only turned the subject-matter of discussion from physics to ethics, but also brought into conscious review the method of philosophising: which was afterwards still farther considered and illustrated by Plato. General and abstract terms and their meaning, stood out as the capital problems of philosophical research, and as the governing agents of the human mind during the process: in Plato and Aristotle, and the Dialectics of their age, we find the meaning or concept corresponding to these terms invested with an objective character, and represented as a cause or beginning; by which, or out of which, real concrete things were produced. Logical, metaphysical, ethical, entities, whose existence consists in being named and reasoned about, are presented to us (by Plato) as the real antecedents and producers of the sensible Kosmos and its contents, or (by Aristotle) as coeternal with the Kosmos, but as its underlying constituents — the ἀρχαὶ, primordia or ultimata — into which it was the purpose and duty of the philosopher to resolve sensible things. The men of words and debate, the dialecticians or metaphysical speculators of the period since Zeno and Sokrates, who took little notice of the facts of Nature, stand contrasted in the language of Aristotle with the antecedent physical philosophers who meddled less with debate and more with facts. The contrast is taken in his mind between Plato and Demokritus.[10]
[9] Aristot. Gen. et Corr. i. 314, a. 6; 325, a. 2; Metaphys. Λ. 1069, a. 25. See the sense of ἀρχαϊκῶς, Met. N. 1089, a. 2, with the note of Bonitz.
Adam Smith, in his very instructive examination of the ancient systems of Physics and Metaphysics, is too much inclined to criticise Plato and Aristotle as if they were the earliest theorizers, and as if they had no predecessors.
[10] Aristotel. Gen. et Corr. i. 316, a. 6. — διὸ ὅσοι ἐνῳκήκασι μᾶλλον ἐν τοῖς φυσικοῖς, μᾶλλον δύνανται ὑποτίθεσθαι τοιαύτας ἀρχὰς, αἳ ἐπὶ πολὺ δύνανται συνείρειν· οἱ δ’ ἐκ τῶν πολλῶν λόγων ἀθεώρητοι τῶν ὑπαρχόντων ὄντες, πρὸς ὀλίγα βλέψαντες, ἀποφαίνονται ῥᾷον· ἴδοι δ’ ἄν τις καὶ ἐκ τούτων ὅσον διαφέρουσιν οἱ φυσικῶς καὶ λογικῶς σκοποῦντες, &c. This remark is thoroughly Baconian.
Οἱ ἐν τοῖς λόγοις is the phrase by which Aristotle characterises the Platonici. — Metaphys. Θ. 1050, b. 35.
The early theorists were studied along with Plato and Aristotle, in the third and second centuries B.C.
Both by Stoics and by Epikureans, during the third and second centuries B.C., Demokritus, Empedokles, Anaxagoras, and Herakleitus were studied along with Plato and Aristotle — by some, even more. Lucretius mentions and criticises all the four, though he never names Plato or Aristotle. Cicero greatly admires the style of Demokritus, whose works were arranged in tetralogies by Thrasyllus, as those of Plato were.[11]
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[11] Epikurus is said to have especially admired Anaxagoras (Diog. L. x. 12).