  A prime example of the interpretative problems facing the student of Plato is the development of his most distinctive doctrine, the theory of Forms. Aristotle, in recounting Plato's intellectual development, reports that “Socrates was the first to seek the universal in ethical matters but that he did not separate it. Plato, marrying Socrates' philosophy with that of Heraclitus, separated the universal, on the grounds that the sensible order, where Socrates had focused, was in flux.” Plato, Aristotle tells us, called these separated universals ‘Forms’ (Metaphysics 1078b12–34). Universal is a technical notion in metaphysics: a universal is that which is predicable of many. It is meant to capture the intuition that a variety of things can all have the same feature or property. For instance, a bowling ball, a basketball, and a figure drawn on a blackboard can all be round. What many things have in common, or a feature they share, is a universal or, in Plato's terms, a Form. Of course there seems to be a huge number of properties. Many different things are white. Many different things are animals. Each (shared) property is a universal—a ‘one over many instances,’ whiteness over the many white things, roundness over the many round things, and so on. Thus, for Plato, Roundness and Whiteness are Forms. Following the lead of Aristotle, scholars have focused on what it means for Plato, in contrast to Socrates, to have separated his universals, the Forms. The starting point, then, for the study of Plato's metaphysics, is the Socratic dialogues and Socrates' investigation into universals of the ethical variety, namely Justice, Piety, Courage and others.