Full Idea
If I only have beliefs about Theaetetus when I don't know his distinguishing mark, how on earth were my beliefs about you rather than anyone else?
Gist of Idea
Without distinguishing marks, how do I know what my beliefs are about?
Source
Plato (Theaetetus [c.364 BCE], 209b)
Book Reference
Plato: 'Theaetetus', ed/tr. Waterfield,Robin [Penguin 1987], p.128
A Reaction
This is a rather intellectualist approach to mental activity. Presumably Theaetetus has lots of distinguishing marks, but they are not conscious. Must Socrates know everything?