By Causality, every F thing (other than the F) is F by partaking of the F. But, by the Piece-of-Pie Model, for X to partake of Y is for X to get a part of Y. Thus, every F thing (other than the F) is F by getting a part of the F. Now let F be the property of being large. In that case, every large thing (other than the large) is large by getting a part of the large. But, Parmenides assumes, if X is a part of Y, then X is smaller than Y (and Y is larger than X), and hence X is (in some way) small. So every large thing (other than the large) is large by getting something small. But this is absurd: as Socrates himself emphasizes at Phaedo 101b, it would be monstrous to say that something is made larger by something small. This is an instance of a general claim we might call “No Causation by Contraries”: