Aristotle in Physics I,1 says some strange-sounding things about how we come to know wholes and parts, universals and particulars. In explicating these, Simplicius distinguishes an initial rough cognition of a thing as a whole, an intermediate “cognition according to the definition and through the elements,” and a final cognition of how the thing’s many elements are united: only this last is πιστήμη. Simplicius refers to the Theaetetus for the point about what is needed for πιστήμη and the ways that cognition according to the definition and through the elements falls short. By unpacking this reference I try to reconstruct Simplicius’ reading of “Socrates’ Dream,” its place in the Theaetetus’ larger argument, and its harmony with other Platonic and Aristotelian texts. But this reconstruction depends on undoing some catastrophic emendations in Diels’s text of Simplicius. Diels’s emendations arise from his assumptions about definitions and elements, in Socrates’ Dream and elsewhere, and rethinking the Simplicius passage may help us rethink those assumptions.