  Socrates’ speech therefore articulates some of the basic elements of the theory of forms, namely Causality and Separation, along with Impurity-S and Purity-F. The theory to which Socrates alludes is richer than his brief description of it suggests. As the dialogue proceeds, the interlocutors invoke a number of additional middle period principles. One principle that plays an important role in the sequel is One-over-Many (see Republic 596a6–7):