Actually people know nothing, except the existence of themselves. "I think, therefore I am" Logic may be false, everything may be false! But I know for sure I exist. Because I am thinking I don't know for certain what thinking is why I am thinking what makes me think what it is I am thinking about, but I think. So there must be at least something and that must be me, whatever 'me' is.
However that was not really the subject of this thread was it?