News You Can Bruise for 2000 June 15

I've been going through On Certainty all morning looking for quotes so that I can piece together Wittgenstein's definition of "mistake" and paint him as an idealist. Here's the fabulous section 430:

I meet someone from Mars and he asks me "How many toes have human beings got?"--I say "Ten, I'll shew you", and take my shoes off. Suppose he was surprised that I knew with such certainty, although I hadn't looked at my toes--ought I to say "We humans know how many toes we have whether can see them or not"?