Nice question. Should science be concerned with "Why" questions, insofar as (it is assumed) they don’t result in measurable observations? As to your initial question:
a. “Are "'why' questions" (broadly understood) useful in or applicable to the study of science? I tend to think that they correspond to a sort of Kuhnian "revolutionary science" which challenges - or at least prods - widely held assumptions”
I agree – “Why” drives scientists to start, and “How” drives science. Taken to its limit, if you’re right, “Why” would be necessary to satisfy the scientists who apply “How”. Moreover, it could be one reason for Kuhnian sorts of revolution (along with, of course, the failure of previous paradigms to account for new experimental results, etc.).
Then, your bases:
b. YOU: First, "why" questions cannot always be reformulated as "how" questions (which appear to be taken as the 'correct' alternative to "why" questions by many at physics.se) without losing the meaning of the question.
Agreed. There is probably a transformational grammar, or table of categories, which might be useful here. Too big for this string, but I’ll make a start below.
c. YOU: Second, it is a false dichotomy to claim that "how" questions are scientific while "why" questions are not: both have natural language examples which correspond to questions in either science or metaphysics.
Agreed. The implicit bias and dichotomy is rather between science and metaphysics. Those “Why” questions which lead to metaphysics are excluded… your third question.
d. YOU: “Third, "why" questions might lead to metaphysics if pursued too doggedly, but used intelligently, "why" questions allow scientists to embrace a curiosity about nature which is an important part of the agonistic method of science which dates back to the ancient Greeks (see the writings G.E.R. Lloyd for an exploration of the "agonistic method" of science).”
But (a necessary condition for your “c”) not all “why” questions lead to metaphysics in a classical sense (Greek or later) – e.g. “Why is there something instead of nothing?” has incited some lively debate in quantum physics… But to avoid confusion, metaphysics ought to be clearly defined, as the example I’ve just given allows for multiple interpretations, including the classical. And maybe spontaneous exclusion of it ought not to occur too hastily. The borders of the two are not cut and dried: that quantum fields are probably unstable and result in “something” still raises the issue of the meta-laws by which that occurs. It creates a border, and both metaphysics and science apply themselves here.
Unless, of course, one takes a strong empiricist line. A confession: I don’t buy that. To paint it as a caricature: Nobody “observes” atoms being split in any conventional sense, but we sure benefit from the nuclear power that drives the PCs of those who disagree. Cutting out the borders to focus on what we know doesn’t really help progress. Not a question to answer here.
This carries over to philosophy. The logical positivist, making claims to science, would exclude “Why” questions as having no meaning, in order to attempt to exclude metaphysics. But clearly the question has meaning, because logical positivists interpret it in order to then discount it; their answer does not account for every sort of meaning. Just so, that “Why” means something to scientists allows for giving the question meaning. Unless one wants to exclude meaning from science. That, for me, would be a pretty poor science.
Note, however, that my claim is normative. I’m just pointing out that it might be worthwhile to follow the “Why”… even in science alone.
So, and next, we could go around for ages on this sort of topic without progress, unless we take a more systematic approach. Herewith some thought-starters:
- The beginning of systematic address begins with clarification. First, “Why” allows for more subdivision than “How”.
Broadly put (and “I put forward for consideration” is implicit in all my declarations): “How” brings the terrain squarely to causality in particular transitions (How does x cause y), and to scientific method when considered as meta-questions and in general (“How should the “how” be interpreted”).
- Second, and my apologies for noting a lacuna in your question. “Why” usually requires “What”, which is as important as “Why”.
Broadly put, “What” constitutes the object of a question (as substantive or intentional), and “How” moves the question to method and causality. They sometimes allow for transformation, often don’t.
Second, “Why” can transform to “How” in some instances (see below), and has standalone value in other cases.
Insofar as “How” moves the question to methodology, it excludes “Why” and “What”. That’s the standard and implicit sense. Too narrow.
So, bref: at the very least, "Why" holds in versions that allow for transition to its counterparts:
- causal (What is the cause of/How has x been caused…)
- Logical (What is the justification for.../How is x to be justified)
But “Why” also holds in fashion that do allow transition to “What”, but no easy transition to “How”, as
- rational (“What is the reason for...”, which could be a principle, motive, etc.) It’s much harder to find a “How” question here.
- teleological (What is the purpose of X). Again, no easy “How” question;
- meaning-orientated (What is the meaning of...).
Each of these allows for subdivision, based upon their semantics, methodical applicability, empirical evidence etc. And each of those subdivisions would allow for multiple refinements of what we exclude (e.g. we don't know the cause of the big bang, and causality might not even have existed then)... and also allow multiple answers as to what we include.
So, no easy answer yet. Just a need for systematisation.