[958]. In Aet. i. 12, where the placita regarding the heavy and light are given, no philosopher earlier than Plato is referred to. Parmenides (fr. 8, 59) speaks of the dark element as ἐμβριθές. I do not think that there is any other place where weight is even mentioned in the fragments of the early philosophers.
[959]. Arist. de Caelo, 308 a 9, περὶ μὲν οὖν τῶν ἁπλῶς λεγομένων (βαρέων καὶ κούφων) οὐδὲν εἴρηται παρὰ τῶν πρότερον.
[960]. Plato, Tim. 61 c 3 sqq.
[961]. Zeller says (p. 876) that in antiquity no one ever understood by weight anything else than the property of bodies in virtue of which they move downwards; except that in such systems as represent all forms of matter as contained in a sphere, “above” is identified with the circumference and “below” with the centre. As to that, I can only say that no such theory of weight is to be found in the fragments of the early philosophers or is anywhere ascribed to them, while Plato expressly denies it.
[962]. The Aristotelian criticisms which may have affected Epicurus are such as we find in de Caelo, 275 b 29 sqq. Aristotle there argues that, as Leukippos and Demokritos made the φύσις of the atoms one, they were bound to give them a single motion. That is just what Epicurus did, but Aristotle’s argument implies that Leukippos and Demokritos did not. Though he gave the atoms weight, Epicurus could not accept Aristotle’s view that some bodies are naturally light. The appearance of lightness is due to ἔκθλιψις, the squeezing out of the smaller atoms by the larger.
[963]. In dealing with Empedokles, Aristotle expressly makes this distinction. Cf. de Caelo, Β, 13, especially 295 a 32 sqq., where he points out that Empedokles does not account for the weight of bodies on the earth (οὐ γὰρ ἥ γε δίνη πλησιάζει πρὸς ἡμᾶς), nor for the weight of bodies before the vortex arose (πρὶν γενέσθαι τὴν δίνην).
[964]. Diog., loc. cit. (p. 390).
[965]. This seems to be in the main the view of Dyroff, Demokritstudien (1899), pp. 31 sqq., though I should not say that lightness and weight only arose in connexion with the atoms of the earth (p. 35). If we substitute “world” for “earth,” we shall be nearer the truth.
[967]. This view was independently advocated by Brieger (Die Urbewegung der Atome und die Weltentstehung bei Leucipp und Demokrit, 1884) and Liepmann (Die Mechanik der Leucipp-Demokritschen Atome, 1885), both of whom unnecessarily weakened their position by admitting that weight is an original property of the atoms. On the other hand, Brieger denies that the weight of the atoms is the cause of their original motion, while Liepmann says that before and outside the vortex there is only a latent weight, a Pseudoschwere, which only comes into operation in the world. It is surely simpler to say that this weight, since it produces no effect, does not yet exist. Zeller rightly argues against Brieger and Liepmann that, if the atoms have weight, they must fall; but, so far as I can see, nothing he says tells against their theory as I have restated it. Gomperz adopts the Brieger-Liepmann explanation. See also Lortzing, Jahresber., 1903, pp. 136 sqq.