  After these, it is normally supposed that Plato’s next two works were the Parmenides and the Theaetetus, probably in that order. If so, and if we take as seriously as Plato seems to the important criticisms of the theory of Forms that are made in the Parmenides, then the significance of the Theaetetus’s return to the aporetic method looks obvious. Apparently Plato has abandoned the certainties of his middle-period works, such as the theory of Forms, and returned to the almost-sceptical manner of the early dialogues. In the Theaetetus, the Forms that so dominated the Republic’s discussions of epistemology are hardly mentioned at all. A good understanding of the dialogue must make sense of this fact.