The term ‘current best scientific theory’ gets thrown around a fair bit. Quineans about ontology say that we ought to believe in the existence of exactly those entities which are the values of bound variables in our current best scientific theory; and metaphysical naturalists argue that metaphysics should be informed by current best scientific theory. In general, epistemological naturalism proposes that our beliefs should be in some way constrained by by current best scientific theory. But what is ‘current best scientific theory’, and why should it play these kinds of normative role?
Start with the obvious. ‘Our current best scientific theory’ is a definite description. Lets take theories to be timeless abstract objects, understood as sets of propositions, and take it that ‘our’ refers back to some non-vague epistemic community. Assume also that ‘scientific theory’ refers to some total theory which is the result of conjoining theories from all of the special sciences. Then ‘our current best scientific theory’ could be disambiguated as follows (I’m not suggesting there aren’t other ways you could read it):
1) Of all the total scientific theories in the public domain, the best one.
2) The total scientific theory which, currently, is considered by some informed majority to be the best in the public domain.
3) The totality of our scientific knowledge.
It is fairly clear that 1) can’t play any very interesting methodological role for grounding ontological commitment. It is consistent with a theory meeting condition 1) that it also be disbelieved and discounted as a serious contender by everybody. So an account of ontological commitment which appealed to best scientific theory understood in the sense of 1) might have us committed to entities in whose existence we flatly disbelieve.
But perhaps 1) can help in explaining the normative role of best scientific theory in guiding philosophical theorizing. If some theory T is in the public domain, and really is the best theory in that domain, then it would be better in some sense to be guided by T than by any other theory in the public domain. But presumably it would be better still to be guided by a true total theory T* which is not in the public domain. The norm ‘be guided by T’ seems just to be a special case of the norm ‘believe the truth’.
If we understand ‘current best scientific theory’ according to 2), then it becomes much more plausible that the norm ‘conform your credences to current best scientific theory’ is one we can in fact follow. Through polls, perhaps, we could collect opinions of experts in various scientific fields, and conjoin them to construct a total theory which informed consensus picks out as the best. Of course, this procedure is highly idealized, but it doesn’t seem entirely impossible for us to build an accurate picture of current best scientific theory, if we understand it according to 2). And if you are persuaded by scientific realism, you will be able to account for the expected good epistemic outcome of following this norm. I think 2) is the standard way of thinking about ‘current best scientific theory’, and underlines much of the use of this phrase in sloganeering.
3) also seems to hold some interest, though. Take ‘current best scientific theory’ to be the common knowledge fragment of the theory given by 2). Since knowledge is factive and sensitive, following correctly the norm ‘conform your credences to the current best scientific theory’ understood according to 3) cannot possibly lead us to false or unreliable beliefs, a risk which is still present with the version of the norm which appeals to 2). Taking ‘current best scientific theory’ in the sense given by 3) yields a norm which seems no harder in principle to follow than Williamson’s conception of knowledge as the norm of assertion.
Conclusions? None really, except that we should try and be precise about what we are talking about in methodological appeals to ‘current best scientific theory’. Depending on how we take that term to pick out a particular set of propositions, we end up with different strengths of epistemic norm. 1) leads to a norm which we cannot in general follow, and 3) leads to a norm which we cannot in general know we are following.
One thing I haven’t considered at all here is exactly how some given total scientific theory should constrain our beliefs. Presumably we don’t want to conditionalize on best current theory, for reasons related to the preface paradox and the pessimistic meta-induction. But saying that we should Jeffrey-conditionalize on it seems to lose all the distinctive force of the naturalist methodology. Perhaps the best way of representing the naturalist credo in Bayesian terms is that there should be some input from current best scientific theory into selecting correct prior conditional credences. But this hasn’t really been thought through at all.
Caveat – I’m still on painkillers after a paragliding incident so the above is probably a little garbled!