What We Know of Language

One of our students posted the following as a comment to another post:

Why must perception, in its definition, state act of apprehending? Must one understand what one sees/views through senses or mind in order for it to be 'perception'?For example: a student who does not speak/read Greek leafs through a Greek text. Can't the student *perceive* that it is in a foreign language, while not *apprehending* its language?

This reminded me immediately of a piece in Plato's dialogue Theaetetus in which the character Socrates is talking with a young man named Theaetetus about language.

SOCRATES: Shall we say that we know every thing which we see and hear? for example, shall we say that not having learned, we do not hear the language of foreigners when they speak to us? or shall we say that we not only hear, but know what they are saying? Or again, if we see letters which we do not understand, shall we say that we do not see them? or shall we aver that, seeing them, we must know them?

THEAETETUS: We shall say, Socrates, that we know what we actually see and hear of them--that is to say, we see and know the figure and colour of the letters, and we hear and know the elevation or depression of the sound of them; but we do not perceive by sight and hearing, or know, that which grammarians and interpreters teach about them.

All this is to say, along with Rachel (I think), that I can know that the letters before me are whatever color. I can know that they have this and that shape, that some are straight and some are curved, etc. I may even recognize them as the letters of a particular language. Given all this, it could be said that I know what I see. I do not, however, as Theaetetus points out, know all that a teacher of the language could tell me about it.