7. Whereof one cannot speak, thereof one must be silent.
In the months before he dies, as winter turns to spring, Ludwig Wittgenstein works steadily, earnestly, and the work is titled On Certainty. Its theme: When does it makes sense to doubt — to ask is that so? is that true? is that real? — and when are doubting questions senseless?

Ludwig does not have the mortal time to rethink, recast, revise, retype, cut, rearrange and rework his words as he has all the obsessive words he leaves in the past. The words come one day after another in small clusters, in similar illustrations ... gnawing on the problem, struggling to make the words evade the shadow of their own mysterious magic and simply show us what he wants us to see.

Wittgenstein writes: "Am I not getting closer and closer to saying that in the end logic cannot be described? You must look at the practice of language, then you will see it."

He writes: "I sit with a philosopher in a garden; he says again and again 'I know that that is a tree,' pointing to a tree that is near us. A second man comes by and hears this, and I tell him: 'This man isn't insane: we're just doing philosophy.'"