Dear L. J-square Wittgenstein,

well, you wonder how we can know that we know?

There is this chaotic collection of notes of yours, called “On certainty”. (You died short after. I hope that this does not refer to readers, too?)

You repeatadly ask the same question: if I see my hand, how can I know that this is my hand? This is your keypoint, right? The question won’t let you go. You are tortured by it. You rephrase and enhance it several times. Such as:

“Why shouldn’t I think of the earth as flat, but extending without end in every direction (including depth)? But in that case one might still say ‘I know that this mountain existed long before my birth.’ – But suppose I met a man who didn’t believe that?”

Ok, I see your point. Furhtermore you mention the challenge to define truth and knowledge if someone thinks (honestly thinks) that he knows something but later it is shown that this was an error.

However, your notes are so chaotic and unsystematic that it is really hard to read them. Or let’s say: Understanding what you wanted to say. Or maybe you  just changed your mind several times during the writing process? Honestly, this is what I think!

Can you not just get out of your grave for a discussion?

By the way, this is my favourite question: How often do we need to check a mathematical calculation in order to be sure that it is correct? Quite my daily problem as a maths student. (Maybe 3x? And it still can be wrong…)

I love it!

[Ludwig Josef Johann Wittgenstein: On Certainty (Über Gewissheit)
ed. G.E.M.Anscombe and G.H.von Wright
Translated by Denis Paul and G.E.M.Anscombe
Basil Blackwell, Oxford 1969-1975]