  According to Purity-F, not only is it the case that the one cannot be both one and many and the like cannot be both like and unlike, but it is also the case that the one cannot be both like and unlike and the like cannot be both one and many. (Notice that Purity-F and Impurity-S together entail Non-Identity, the claim that no form is identical to any sensible thing. A similar form of argument appears at Phaedo 74b–c, a passage in which Socrates argues that whereas sensible things that are equal are also unequal, the equal is not unequal, and hence the equal is not identical to any equal sensible thing.)