This paper is a restatement of my earlier analysis of this argument (1954), Revised in the light of critical comments by other scholars and of closer study of the text. It includes a critical discussion of an alternative formalization of the argument, First offered by wilfrid sellars (1955) and retained (with modifications) by colin strang (1963), Which eliminates successfully the inconsistency of the premises of the argument but has dubious support from plato's text.