A Summary

The world is permitting us to have the conversation we are having now. Within this conversation, we can say things about the world (for instance, that it is permitting us to have this conversation). Some of these things we say about the world are, literally, undeniable.

Any statement which renders conversation impossible whenever we attempt to take it seriously must be at least false. The contraries of some of these statements must be true in any intelligible language - they are Barry Stroud's 'privileged statements'. (This circumstance also elucidates puzzles like 'Moore's paradox'.) The intelligibility of our present conversation is the fulcrum on which our capacity to talk about the world turns.

We cannot intelligibly deny that we are having a conversation, because if we are not having a conversation then we can't explicitly 'deny' anything at all. You might imagine that any of us could 'deny' it privately - as a thought, rather than as a statement in a shared conversation. This 'denial' would have to either (a) be 'non-linguistic' or (b) be articulated in some 'private language' which cannot in principle be used for public conversation.

It's worth reminding ourselves here of the role of interpretation, and of how we attribute intentional states. If  you tell me you believe something, and I acknowledge you as an honest and competent interlocutor, then I must accept your statement as irrevocable evidence of your intentional state with respect to that belief. To do otherwise is to doubt your honesty or competence - to doubt the quality of your participation in our conversation. In other circumstances, we can only attribute beliefs to one another hypothetically and corrigibly - perhaps on the basis of behaviour, or on other 'indirect' evidence. It is therefore impossible to unequivocally attribute the belief that conversation is impossible, since it can never be articulated within a conversation. This means that alternative interpretations of the evidence are always intelligible.

At the very least, we can do without being able to attribute such a belief. If we also want to do without 'private languages', then we must.

In general, to have an intelligible thought is to have a thought that can, in principle, be shared in a conversation. We have many 'unintelligible thoughts' - in the sense of more-or-less conscious mental processes - which seem, subjectively, to viscerally drive our capacity to converse in certain ways.  This is why we imagine that our 'inner experience of the world' must be a validating ground of what we say. This subjective 'ground' is not directly shared with our interlocutors, however, so we can neither point to it as evidence nor fully explain its role in driving our 'linguistic behaviour'. As Hume observes, we may be compelled by it but we cannot validate our compulsion. This is, if you like, what it 'feels' like to be a language user, what it feels like to be able to converse. We cannot use it to justify what we say.

One implication of the intelligibility of our conversation is that many statements beyond the ones within this conversation must also be intelligible. To deny this would make our present conversation unintelligible. 'Only what we are saying now makes sense' cannot make sense - at the very least because it denies the sense of any further discussion of what counts as sense-making. The individual parts of our conversations 'work' only as elements in networks of other experiments with sense-making. Quine and Davidson (among others) thought something like this, but made a mistake about how it came about.

The nodes in these networks are linguistic moves, and the links are meaning rules and truth conditions (or conditions of legitimate use).  We discover them through linguistic experiment, through exploring what we find intelligible. Some experiments lead to the collapse of any possibility of network construction - sometimes directly and sometimes very indirectly indeed.

We cannot construct a 'complete and final' model of this network, as this would generate an open question paradox. 'This is a complete and final description of the way we use language' can only be made sense of as a node in the network it claims to validate. On the other hand, 'we cannot explore any aspect of this network' cannot be a node in any intelligible semantic network.

There is no 'explanation' of how we come to have conversations that can validate the having of conversations. All explanations take place within conversations - our ability to converse validates our explanations, not vice versa. Within specific contexts, and sometimes in the context of the possibility of conversation in general, some explanations turn out to be the only ones that are intelligible.

With respect to the general validity of our scientific conversations, we can say that they are at least 'permitted' - that the world allows us to talk about it in the way that we do. What we find, though, is that 'We can talk as though X is true' and 'X is true', taken unconditionally, share the same truth conditions. On some accounts, this would imply that they 'mean' the same thing, although some metaphysical thinkers might find this objectionable - especially, perhaps, theologians.

(I am reminded, again, of Robert Winston's response to Richard Dawkins' question about how a 'man of science' like himself can believe in God: "I'm going to give you a very Jewish answer: it depends on what you mean by ''God'.")

And that's more or less it. The solution to a problem first posed by the Greeks ...