  In what way does the existence of an infinite regress of forms represent a problem for the theory of forms? One answer to this question (see Vlastos (1954, 328, fn. 12; 1955), Goldstein and Mannick (1978), Penner (1987, 279–282), and Fine (1993, 204)) is that the nature of the problem is fundamentally epistemic. On this view, the theory of forms includes the thesis that, for any property F, the primary function of the F is to explain the F-ness of F things, and hence to make it possible for humans to apprehend and know things as F. But, so the story goes, Plato assumes that an infinite regress of forms of F-ness, each of which explains the F-ness of the forms of F-ness below it in the hierarchy, cannot explain the F-ness of the original plurality of F things: explanation must come to an end somewhere. Although this interpretation makes sense of the epistemic language that Plato sprinkles throughout the Third Man passage, it does not make sense of the fact that Parmenides sets up the argument by pointing out that the oneness of the large follows from its being one “over” many large things (see above). So it is unlikely that the epistemic reading of the Third Man is what Plato had in mind.