You don't know what you don't know.

Je sais que je ne sais pas ce que je ne sais pas.

If I don't know I don't know, I think I know.
If I don't know I know, I think I don't know.

The only thing I know is that I know nothing, and i am no quite sure that i know that.

I am likely to be wiser than he to this small, extent, that I do not think I know what I do not know.

All I know is that I do not know anything

Perhaps my greatest wisdom is the knowledge that I do not know.

Can you disbelieve in something you don't know about? […] It isn't that I don't believe but that I don't know.

Not only do I not know what's going on, I wouldn't know what to do about it if I did.

The unknown words remind me that there's a lot I don't know in this world.

I don't know. I don't know at all. And that's what's frightening the life out of me. To have no idea....

Surely this is the objectionable kind of ignorance, to think one knows what one does not know? But in this, gentlemen, here also perhaps I am different from the general run of mankind, and if I should claim to be wiser than someone in something it would be in this, that as I do not know well enough about what happens in the house of Hades, so I do not think I know.

He who thinks he knows, doesn't know. He who knows that he doesn't know, knows.

Well, although I do not suppose that either of us know anything really beautiful & good, I am better off than he is- for he knows nothing & thinks that he knows; I neither know nor think that I know.