There are only a few places in the entire Platonic corpus in which Socrates claimed to know anything, at least as far as I have been able to discover:
1. “I claim to know nothing aside from erotic matters…” — Symposium, 177d. (Ta erotika could also be rendered variously, “erotic things,” “the erotic,” “erotic matters”)
2. “It is certainly not conjecture to say that right opinion and knowledge are different. There are few things I would claim to know, but that is among them at least…” — Meno, 98b
3. “Come then, tell me this, [Euthydemus] said: Do you know anything? Certainly, [Socrates] replied, many things, though trifling.” — Euthydemus, 293b. (The relevant objects of knowledge are qualified as polla, i.e. “many,” and as smikra, which is “small” or “unimportant” or, as I have rendered it in my translation, “trifling.”)
4. “I am wiser than this man, for neither of us seems to know anything great and good; but he imagines that he knows something, even though he knows nothing; whereas I, not knowing anything, do not believe that I do. In this trifling thing (smikron) then, I seem to be wiser than he is, because I do not believe that I know what I do not know.” — Apology, 21; (It must be said that this is the closest as Plato’s Socrates ever gets to saying, “I know that I do not know.” Literally, this is not what is said, although it is not clear how recognizing one’s lack of knowledge could ever be doubtful if recognized at all. Notice that this recognition of a difference between himself and the one claiming wisdom is also called a “trifling thing.”)
Is there some way in which Socrates’ few admitted objects of knowledge — (i) the difference between opinion & knowledge, (ii) erotic matters, (iii) many trifling things, and (iv) one’s own ignorance — are related in some way?