If I say of myself that it is only from my own case that I know what the word "pain" means -- must I not say the same of other people too? And how can I generalize the one case so irresponsibly?

Now someone tells me that he knows what pain is only from his own case! Suppose everyone had a box with something in it: we call it a "beetle". No one can look into anyone else's box, and everyone says he knows what a beetle is only by looking at his beetle. -- Here it would be quite possible for everyone to have something different in his box. One might even imagine such a thing constantly changing. -- But suppose the word "beetle" had a use in these people's language? -- If so it would not be used as the name of a thing. The thing in the box has no place in the language-game at all; not even as a something: for the box might even be empty. -- No, one can 'divide through' by the thing in the box; it cancels out, whatever it is.

That is to say: if we construe the grammar of the expression of sensation on the model of 'object and designation' the object drops out of consideration as irrelevant.

-- Ludwig Wittgenstein, Philosophical Investigations