Socrates
SOC. The second is this: knowing one of you and not knowing the other, and not perceiving either of you, I never could think that the one whom I know is the one whom I do not know.
5
Socrates
SOC. And this is the third case: not knowing and not perceiving either of you, I could not think that he whom I do not know is someone else whom I do not know. And imagine that you have heard all the other cases again in succession, in which I could never form false opinions about you and Theodorus, either when I know or do not know both of you, or when I know one and not the other; and the same is true if we say perceive instead of know. Do you follow me?