I pseudo-agree with Decartes that the 'self' can be known to exist. What I meant by "no one knows anything about anything" I meant anything outside one's own mind.

​

But you raise an interesting point, because I only pseudo-agree with Decartes. I believe a more extreme conclusion than "I think therefore I am" should be reached if we are unwilling to make assumptions. What I propose:

I think, therefore I know something exists. That thing could be "me", but "me" may not be what I think it is. To me, it seems the phrase "I think therefore I am" presumes knowledge of one's self, which if we're unwilling to make any assumptions whatsoever, shouldn't be presumed. For example, "I" might be a deterministic simulation run by some other guy that has not made his existence known to me. In that case, if I am a deterministic simulation, if I have no free will (by free will I mean the free will to have my own thoughts, by thoughts I don't mean beliefs, I mean mere cognitions. If I'm not capable of making my own cognitions) then I would claim that I "don't exist", in the sense that I don't exist in the way I think I do, and I don't exist as an independent being, rather, I'm a subset of some other object (in this case a simulation).