“Do you know what it means that W. behaves as he does but sees nothing; & on the other hand that he sees?”
  If you ask yourself this & answer ‘yes’ you conger up some sort of image. This image is it seems derived
from the fact of your seeing or not seeing (if you close your eyes) & by this derivation, it seems, it must be the picture we interpret to correspond to our sentence “he sees”, “he doesn't see”. – As when I substitute my body for his body & for holding a match holding a pen. – But substituting his body for my body might mean that my body has changed so as to be now like his, & perhaps vice versa. It seems a direkt & simple thing to understand “knowing thinking that he has what I have” but it isn'tt at all. The case is simple only if we speak e.g. of physiological processes. “I know only indirectly what he sees but directely what I see.” embodies an absolutely misleading picture. I can't be said to know that I have toothache if I can't be said not to know that I have toothache. I can't be said to know indirectely that the other has if I can't be said to know it directely. The misleading picture is this I see my own machbox but know only from hearsay what his looks like. We can't say: “I say he has t. because I observe his behaviour but
I say that I have because I feel it”. (This might lead one to say that ‘t.’ has two meanings, one for me & one for the otherˇ being)
  “I say ‘I have t’ because I feel it” contrasts this case with, say, the case of acting on the stage but can't explain what ‘having t’ means because having t = feeling t & the explanation would come to “I say I have it because I have it”. = I say I have it because it is true. = I say I have it because I don't ly. One wishes to say: In order to be able to say that I have t. I don't observe my behaviour, say in the miror. And this is correct, but it doesn't follow that you d[i|e]scribe an observation of any other kind. Moaning is not the description of an observation. ˇThat is You can't be said to derive your expression from what you observe. Just as you can't be said to derive the word ‘green’ from your visual impression but only from a sample. – Now against this one is inclined to say: “Surely if I call a colour green I don't just say that word, but the word comes in a particular way”, or “if I say I
have toothache’ I don't just use this phrase but it must come in a particular way!” Now this means nothing for, if you like, it always comes in a particular way. “But surely seeing & saying something can't be all!” Here we make the confusion that there is still an object we haven't mentioned. You imagine there is a pure seeing & saying & one + something else. Therefore you imagine all distinctions to be made as between a, a + b, a + c, etc. The idea of this addition is mostly derived from considerations of our bodily organs. Wh All that ought to interest you is whether I make all the distinctions which you make: whether e.g. I dont distinguish between [s|c]heating & telling the truth. – “There is something else!” – “There is nothing else!”. ‒ ‒ ‒ “But what else is there? – “[B|W]ell this→!”.
  “But surely I know that I am not a mere automaton!” – What would it be like if I weren't? – “How is it that I can't imagine myself not seeing, hearing etc. experiencing?” – We constantly confuse & change about the comon sense use & the metaphysical use.

  “I know that I see.” –
  “I see.” – you seem to read this off some fact; as though you said: “There is a chair in this corner.”
  “But if in an experiment, e.g. I say ‘I see’ why do I say so? surely because I see!”
  It is as though our expressions of personal experience needn't even spring from [c|r]egularly recurrent inner experiences but just from something.
  Confusion of description & sample.