of such a kind that the grounds that he can give are no surer than his assertion, then he cannot say that he knows what he believes.
 If someone says "I have a body", he can be asked "Who is speaking here with this mouth?"
 To whom does anyone say that he knows something? To himself, or to someone else. If he says it to himself, how is it distinguished from the assertion that he is sure that things are like that? There is no subjective sureness that I know something. The certainty is subjective, but not the knowledge. So if I say "I know that I have two hands", and that is not supposed to express just my subjective certainty, I must be able to satisfy myself that I am right. But I can't do that, for my having two hands is not less certain before I have looked at them than afterwards. But I could say: "That I have two hands is an irreversible belief." That would express the fact that I am not ready to let anything count as a disproof of this proposition. 
 "Here I have arrived at a foundation of all my beliefs." "This position I will hold!" But isn't that, precisely, only because I am completely convinced of it? - What is 'being completely convinced' like?
 What would it be like to doubt now whether I have two hands? Why can't I imagine it at all? What would I believe if I didn't believe that? So far I have no system at all within which this doubt might exist.
 I have arrived at the rock bottom of my convictions. 
And one might almost say that these foundation-walls are carried by the whole house.
 One gives oneself a false picture of doubt.
 My having two hands is, in normal circumstances, as certain as anything that I could produce in evidence for it.
That is why I am not in a position to take the sight of my hand as evidence for it.
 Doesn't this mean: I shall proceed according to this belief unconditionally, and not let anything confuse me?
 But it isn't just that I believe in this way that I have two hands, but that every reasonable person does.
 At the foundation of well-founded belief lies belief that is not founded.
 Any 'reasonable' person behaves like this.
 Doubting has certain characteristic manifestations, but they are only characteristic of it in particular circumstances. If someone said that he doubted the existence of his hands, kept looking