...If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain. - Yes, but after all not with the certainty with which I know it myself! - It can't be said of me at all except (perhaps as a joke) that I know I am in pain. What is it supposed to mean - except perhaps that I am in pain?
Other people cannot be said to learn of my sensations only from my behaviour,—for I cannot be said to learn of them. I have them.
The truth is: it makes sense to say about other people that they doubt whether I am in pain; but not to say it about myself.
"Only you can know if you had that intention." One might tell someone this when one was explaining the meaning of the word "intention" to him. For then it means: that is how we use it.
(And here "know" means that the expression of uncertainty is senseless.)
I heard it said yesterday, at a conference, in the context of a discussion of John Hyman's analytical-philosophical 'account' or 'conception' (i.e. that project of answering the question 'what is something?' by citing general sufficient conditions or general proper definitions) of knowledge that p as having an ability to use (or be guided by) the fact that p as a reason (for doing or saying something), that Wittgenstein did not in fact give us reasons for thinking that 'It can't be said of [myself] that I know I am in pain'. And in the context of that discussion I took it that Wittgenstein was - aside from some possible face-saving reconstruction by Anthony Kenny - being taken to be failing to offer something which anyone, including Wittgenstein himself, might have thought sensible to offer - namely for him to say to us 'here is my general positive conception of knowledge, and behold, here we see that the alleged first person case of knowledge does not fall under that conception.' (... The point being that, by contrast, on Hyman's general 'account' of knowledge the person who says 'I know I am in pain' is perfectly entitled to say this since they may of course use the fact of their being in pain as a reason (why didn't you play badminton this week? I had a pain in my elbow).)
Yet one of the things which is clear from 247 is that Wittgenstein is not in fact always shy of letting us know what he takes 'know' to mean. ('And here "know" means that the expression of uncertainty is senseless.') And, in fact, given that this remark occurs in the very passage after the one in which he says that it can't be said of myself that I know I am in pain, the situation is really rather curious. After all is he really saying that it can't be said of myself that an expression of doubt by me regarding my sensation is senseless? That in fact would seem to be rather the opposite of what he is claiming!
What is going on here? First of all, why can't it, joking aside, be said of me that I know that I am in pain? Second, how can it be true that this can't be said when in the very next paragraph we are offered a use for 'know' which looks like it makes for the possibility of what was denied in the previous paragraph?
The trick to answering or perhaps, better, dissolving these questions is to note that Wittgenstein is not interested in providing general sufficient conditions. Nothing in what he says about our life-with-language would lend support to the idea that he thought that an intelligible philosophical project. He is at times (as in 247 concerning know and intention) happy to provide contextually situated sufficient conditions ('And here 'know' means...'), but nowhere does he defend the (to me intuitively implausible - but you might have other ideas!) notion that language is trans-situationally decomposable. As if, for example, one might intelligibly imagine someone who went through his earlier life never hearing the word 'know' used, but being perfectly proficient in understanding and deploying facts as reasons, could then be inducted into our knowledge talk at one fell swoop. (One natural thought is: might we not expect to encounter analogues of Gettier-type problems for Hyman's non-belief-involving account of knowledge? That is, cases of being 'guided by' facts in offering reasons, or however exactly the proposal is to be cashed out, which don't amount to knowledge or which tacitly and illegitimately build in a reference to knowledge in order to secure their fix on their target.)
But then, it might be suggested, the problem with 246 is not just that no general account of knowledge is given, but that we don't even have a specific account of what talk of 'knowledge' in the context of sensations would be. But then that seems absurd too. After all, if Wittgenstein had such a specific account then he could hardly go on to say that it is nonsense to talk here of knowledge! So what does he mean? What I propose (in a 'new Wittgensteinian' spirit) is that, far from saying that something in our general concept of knowledge rules out a coherent application of it to cases of my own relation to my own sensations, he is saying that nothing here has yet been 'ruled in' (as it were). That is, he is claiming, there is no obvious use to talk here of 'knowing that I am in pain', nothing that comes to mind when we try to imagine here what those words are supposed to be doing, no obvious contribution they make to our conversations, nothing they add to my merely saying 'I'm in pain'.
Is Wittgenstein trying to say that we can't imagine uses for 'I know I am in pain'? In fact I think we can imagine uses for that sentence. For example you might be quizzing me about my grasp of the concept 'pain' and I kick myself and say to you 'I know I am in pain'. It's a bit odd, perhaps, but it seems to me not unimaginable. (We might also imagine someone insisting, to someone who is wrongly trying to generalise a situationally unhelpful conception of reason-giving to argue down someone who tries to appeal to their pain as a reason not to go into work, that they know they are in pain. Again, it's a bit odd, but I think we can probably get there!) Here I have made sense of the idea of knowing I am in pain by imagining a possible situationally specific use of the sentence. And surely - and this is the general 'new Wittgensteinian' point - nothing stops us from developing uses which, so long as we demonstrate them, show the contributions they can make to our conversations, are perfectly and (as it were) unaccountably fine. What he was disputing was not that we can't ever imagine helpful deployments of 'I know I am in pain' but that, in the context of our relation to the fact that I am in pain, talk of 'knowledge' seems to have yet no clear work to do.
But, you know, feel free to invent some such a purpose. Wittgenstein surely wouldn't want to stop you! After all, he's got no general account about which to get defensively protective.