  The third proposed account of logos says that to give the logos of O is to cite the sêmeion or diaphora of O. In the Wax Tablet passage, sêmeion meant ‘imprint’; in the present passage, it means the ‘sign’ or diagnostic feature wherein x differs from everything else, or everything else of O’s own kind. So, presumably, knowledge of (say) Theaetetus consists in true belief about Theaetetus plus an account of what differentiates Theaetetus from every other human.