Do I know something about my self?

Of course I do. I may be wrong about this being a crazy summer day, with the sun fighting to come out but being repeatedly chased and suffocated by black, thundering clouds. I may be wrong about there being a screen in front of me. And I may be wrong about these being fingers on the keys, or their being mine. I can imagine situations in which none of these beliefs are true. But no situation can be imagined in which it is false that I see black thundering clouds, or that i feel pressure as if i had fingers and they were hitting keys. This knowledge cannot be denied. Not only is it the rock bottom of what I know, it is also top quality as far as what I can know