  Unitarians can suggest that Plato’s strategy is to refute what he takes to be false versions of D3 so as to increase the logical pressure on anyone who rejects Plato’s version of D3. In particular, he wants to put pressure on the empiricist theories of knowledge that seem to be the main target of the Theaetetus. What Plato wants to show is, not only that no definition of knowledge except his own, D3, is acceptable, but also that no version of D3 except his own is acceptable.