11/19/2007

Can a widespread local realist be a global anti-realist?--and the preface paradox

I have been thinking about whether there might be something like the preface paradox in the scientific realism debates. There is now a distinction being drawn between local (or 'retail') realism, in which one argues for the truth of particular scientific theories (e.g. quantum mechanics) or the existence of particular scientific entities (e.g. quarks), on the one hand, and global (or 'wholesale') realism, in which one argues for the approximate truth (or referential success) of mature scientific theories in general.

What I'm wondering is whether it can be justified and/or rational to be an everywhere local realist (so QM is approximately true, and general relativity is approximately true, and population genetics is (approximately) true, etc.), but still be a global anti-realist -- say, because you place a lot of weight on the pessimistic induction on the history of science. Or, on the other hand, whether everywhere local realism really pushes us towards global realism.

I'm currently guessing that one CAN be an everywhere local realist without being a global one, for the following two reasons.
(1) One standard response to the preface paradox seems perhaps even more applicable here than in the preface case: while the author assigns a high probability to each individual assertion in her book, the probability of (p & q & r & ...) will be low.
(2) Also, although if A is true and B is true, then 'A and B' must be true, it seems to me that even if A is approximately true and B is approximately true, then 'A and B' need not be approximately true, for A and B could be contradictory (for example, the prima facie conflict between quantum mechanics and general relativity).

I'm happy to hear any reasons for the opposite view, viz. that widespread local realism pushes us towards global realism.

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7 Comments:

At 19/11/07, Anonymous Anonymous said...

Do you mean that the answer is yes? Or are you answering the opposite question? I assume it's one of the two, given the arguments you've put there.

-Kenny (google wouldn't let me sign in right for some reason)

 
At 20/11/07, Blogger Greg said...

Hi Kenny --

Thanks, I was unclear. The answer is yes; I've modified the original post to make that obvious.

 
At 29/11/07, Anonymous Anonymous said...

Hello greg,

It seems that such a position would be consistent, but how would you motivate it? You mentioned the PMI, but that won't work: putting weight on the PMI will push you toward instrumentalism in each individual case as well as globally. Unless you can argue for privileging a particular theory.

Marco

 
At 29/11/07, Blogger Greg said...

Hi Marco --

Thanks for stopping by, and for the question -- it's a good one, since I didn't explain why someone might want to hold this position.

I don't have a fully worked-out position, but I was thinking: if there is a massive amount of evidence for a particular theory, from several independent sources of evidence, then you might want to say that theory is (probably and approximately) true. (Yes, you could be wrong, but you could be a brain in a vat as well.) It's that simple: believe things there's a massive amount of evidence for.

The bigger picture here for me is this: I have a specific argument against the 'no-miracles argument' for scientific realism. One of the philosophical options left, if my argument is accepted, could be a local realism but global anti-realism.

Thanks again!

 
At 29/11/07, Blogger marco said...

Greg, I take your position to be something like:
(1) The PMI has force
(2) the NMA lacks force
(3) Global anti-realism (follows from [1] and [2])
But:
(4) Particular theory T1 is eminently supported, so we are realists about T1.

Now, I am sometimes skeptical about the relevance of the global debate for particular theories. But it seems to me has to be the case that:
(A)if realism about T1 is supported, it is on explanationist lines. If these grounds are good here, they're good anywhere. So global realism beckons.
(B)the PMI works, if it does, because there have been massively supported theories which were eventually replaced. So antirealism about T1 beckons.

I think there is a stable position close to what you propose: accept both PMI and NMA, and accept various strengths of semirealism depending on the theory; a fairly strong one, then, for T1.

 
At 29/11/07, Blogger Greg said...

Hi again, Marco --

Thanks, that's helpful. I can explain now exactly where I want to part ways with the dialectic you've sketched above.

I grant that particular scientific theories are accepted on broadly explanationist lines. But I argue that the NMA appeals to a crappy explanation, that does not meet the standards scientists usually require explanations to meet.

Short explanation: in the NMA, scientific realism explains only one previously accepted fact, viz. the instrumental success of science. Scientists usually do not accept such explanations. For a fuller account and defense of my view, see this post I wrote last year -- which I should've linked to in my last comment.

 
At 26/2/08, Blogger Greg said...

Note to self --

It is not clear what global realism should be. Two options (where T1 etc. are mature scientific theories):

(1) [assumed in post] Pr(T1 & T2 & ...) is reasonably high.

VS.

(2) If Ti is drawn randomly from the set of mature scientific theories, then Pr(Ti) is reasonably high.

It now seems to me that a realist would probably want to say something more like (2), not like (1).

 

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