.W., believe, am sure, that my friend hasn't sawdust in his body or in his head, even though I have no direct evidence of my senses to the contrary. I am sure, by reason of what has been said to me, of what I have read, and of my experience. To have doubts about it would seem to me madness - of course, this is also in agreement with other people; but I agree with them.
 I cannot say that I have good grounds for the opinion that cats do not grow on trees or that I had a father and a mother.
If someone has doubts about it - how is that supposed to have come about? By his never, from the beginning, having believed that he had parents? But then, is that conceivable, unless he has been taught it?
 For how can a child immediately doubt what it is taught? That could mean only that he was incapable of learning certain language games.
 People have killed animals since the earliest times, used the fur, bones etc.etc. for various purposes; they have counted definitely on finding similar parts in any similar beast.
They have always learnt from experience; and we can see from their actions that they believe certain things definitely, whether they express this belief or not. By this I naturally do not want to say that men should behave like this, but only that they do behave like this.