Determinism, Prediction

The metaphor of universal determinism is based on our ability to predict and/or control the behaviour of some parts of the universe. We presume, from our knowledge of this ability, that the whole behaves like these parts.

I've hinted at why this must be wrong before, and also at some problems with the perspective that I've tried to take. What I want to do here is to draw attention to the the central incoherence of the metaphor.

First, it is a metaphor which is impossible, in principle, to completely unpack. It doesn't matter how much computing power we have, the machinery which implements it will be part of the universe we are trying to predict, and so would be subject to the halting problem (the open question paradox as it appears in algorithmic processing). The machine could not predict relevant aspects of its own behaviour.

Secondly, our predictive theories are captured in a semantic net which cannot, itself, be completely analysed. This is because this analysis must depend on semantic assumptions. Even the law of non-contradiction can only be stated in words.

I've mentioned the necessity of attributing agency to interlocutors, and the problems this creates for universal determinism. There is more to the semantic dimension than this, though. The Kripke/Goodman paradox shows us that there will always be competing semantic interpretations of any finite set of mechanical signals. And yet it is only mechanical processes (and signals) that a universal determinism can predict. No determinism can, therefore, predict the correct interpretation of, for example, a string of characters. This means that no determinism can absolutely establish the correct interpretation of any string of characters which might be taken to be a statement of universal determinism. There is no determinism which allows us to give an unequivocal semantic account of itself.

In some respects, this might be bundled in with other catastrophic implications of the Kripke/Goodman paradox - one of which seems to be that we cannot give an unequivocal account of anything at all. The worst of these implications can, however, be resolved within a recursive account of truth-telling, and a proper understanding of the irreducibly semantic character of whatever conversation we are having now.

This kind of solution is very unfriendly to the deterministic metaphor, however. It puts semantic, rather than mechanical, characteristics at the roots of our explanations and predictions. Also, because our conversations must take place 'in the world' the idea that there is a perspective from which a universal determinism could be demonstrated is incoherent. Not only is there no god-like perspective, but no being with such a perspective could have a private language any more than the rest of us. And certainly not one we could ever learn to speak...

The incoherence of the mechanical metaphor doesn't, at first, seem particularly relevant to the problem of logical determinism, which arises from the fact that the truth-value of a properly contextualised statement about the world - even if it is about the future - cannot vary. If it turns out to be the case that I live into my eighties, then our conventional understanding of the logic requires that this was always the case, but that we just didn't know until the relevant bits of the future had been properly examined. Letting the truth-values of properly contextualised statements vary breaches the rule of non-contradiction, which strikes at the very heart of intelligible semantic processing.

This seems to be a grammatical matter, however, and possibly less consequential for the attribution of agency, since that seems to be as necessary to semantic processing as the invariability of truth values.

The problems with the mechanical metaphor may have this relevance, mind you: that there are factual statements about the future whose truth values cannot in principle be determined from current facts. This gives the 'truth value' a very abstract flavour. It also means that the logical grammar will never undermine the 'use-meaning' of these statements, or of anything intelligible we might care to say about how we attribute truth-values to them, or about what we mean when we do. Preserving the rule of non-contradiction here can have no awkward practical consequences, and any time it seemed threatened re-contextualisation would remove the threat.