Stroud again ...

Barry Stroud's exact error is that he thought a wedge could be driven between 'X is true' and 'We can in all respects converse as though X were true'. He missed the real force of Wittgenstein's 'beetle' argument.

'X is true', in other words, literally means that we can, in all respects, converse as though X were true. No sense can be attached to it otherwise.

We might imagine that a 'thought' can be true, or a 'proposition' can be true, independent of language. But this is exactly to imagine that the contents of my box must be the 'same' as the contents of your box for our discourse to be meaningful. In fact, issues of 'sameness', and even the concept of 'sameness' itself can only arise within a functioning discourse.

'Sameness' is, fundamentally, a semantic concept. When we say 'we can only speak to one another because there are some things in the world that are the same as one another', we are arguing that sameness 'in the world' can be deduced from our ability to converse.

Our ability to converse is the fulcrum - not some fact about the world. If there is a 'verificationist principle' at work here, it is the possibility of verification itself - the possibility of producing an intelligible account of anything at all.

Our private phenomenological space is, to a relevant extent, radically unshareable. When we make it the locus for intentional states, we do no more than claim that we can talk to one another. When we attribute intentional states to those with whom we cannot converse (our pets, for instance) we are no more than saying 'if they could talk, they would talk this way'.

I can only ask a philosophical question in a functioning conversation. The idea of a philosophical question about whether it is possible to have a functioning conversation is unintelligible. We would need a 'private' language in which to ask such a question, and such a language would only be intelligible if it could, in principle, be shared.