[95] I have in preparation a study of the problem of physical interaction in Pre-Socratic philosophy which deals with this question in all its phases.
[96] This statement is, of course, figurative, since Empedocles denied the existence of a void.
[97] I cannot now undertake a defense of this statement, which runs counter to certain ancient reports, but must reserve a full discussion for my account of physical interaction.
[98] The motive for making this assumption was clearly the desire to make of the Νοῦς the prime mover in the world while exempting it from reaction on the part of the world, which would have been unavoidable if its nature had contained parts of other things. It is the same problem of "touching without being touched in return" that led Aristotle to a similar definition of God and of the rational soul. The same difficulty besets the absolutely "simple" soul of Plato's Phaedo and the causality of the Ideas.
[99] Aristotle, De Generatione et Corruptione, 323b 10 f.
[100] We have seen that this distinction was latent in Anaximenes's process of rarefaction and condensation. For other matters see Chaignet, Histoire de la Psychologie, Vol. I, p. 114, whose account, however, needs to be corrected in some particulars.
[101] I say "perhaps" because ancient reports differ as to the precise relation of position and arrangement to the distinction between qualities, primary and secondary.
[102] This is only another instance of what Mr. Venn (Empirical Logic, p. 56) has wittily alluded to as "screwing up the cause and the effect into close juxtaposition."
[103] Simplicius says εὐθὺς μετὰ τὸ προοίμιον; see Diels, Die Fragmente der Vorsokratiker (Berlin, 1903), p. 347, l. 18.
[104] Fr. 2, Diels.