Horgan on Common Sense

19 08 2005

There’s an interesting discussion between John Horgan (of The End of Science fame – a very interesting set of interviews with scientists and philosophers of scientist, and a bit amateurish in terms of the content, as one might expect – I recall it as being worth reading though) and Leonard Susskind (a relatively important physicist and string theorist, from what I see) and several others (whose points are less interesting) about string theories and the ability of common sense to lead us to reject them. I’m not (yet) a philosopher of science, but it seems that Horgan is onto something – scientific theories can’t be totally unconstrained by some sort of reasonableness. But I think he’s definitely wrong on this particular point. I’m not a believer in Penelope Maddy’s position that “philosophy cannot criticize [nor] can it defend” science. But this is because I think philosophy and science are continuous with one another, and each should be able to shed light on the other. However, it has to be done far more carefully than Horgan is doing it here. Susskind seems to make this point quite eloquently by talking about “uncommon sense”.

At the end, Horgan repeats the common complaint about string theory that it’s not experimentally falsifiable or confirmable. According to Susskind (and I certainly can’t say myself) this just isn’t the case. But even if Horgan is right about it’s non-testability, I assume he means it in the sense that there is no experiment that could confirm or verify string theory as against the contemporary mix of quantum mechanics and relativity. I would be surprised if the theory was totally unable to be falsified or confirmed at all. Even if different settings of parameters make the theory consistent with different numbers of fundamental particles, different sizes of the universe, and so on, I assume that these parameters will have to be set to account for some amount of the observations one has, and once they’re set, they would make further predictions approximately in line with current scientific theory, and not just allow for all the seeming laws to suddenly change at any moment. I certainly hope string theory is verifiable or falsifiable in at least this weak sense – this seems like an important criterion for scientific theories (though the Quine-Duhem problem shows that we need to be somewhat more careful in phrasing this weak requirement).

But there is no important need for this stronger sense of falsifiability and confirmability (that is, the kind that requires there to be some experiment to differentiate it from current theory). Sure, it would be nice to be able to have an experiment to settle which one of the two theories was better, but even if there’s not, that doesn’t mean the new theory isn’t scientific. That would make science too much a matter of historical accident – the Copenhagen Interpretation of quantum mechanics would be science, but the many-worlds theories and Bohm’s theories would be dismissed as unscientific. If they had come in a different order, a different one would have been scientific. And even apart from this problem, it seems there are often benefits to debating two theories that are empirically identical. Oftentimes, one theory will suggest different modifications in the face of recalcitrant evidence. Or one theory will make all the calculations far easier. Or one theory postulates fewer invisible elves pushing electrons around, and otherwise fits together more aesthetically.

This is the sort of debate in which philosophy and common sense (or perhaps better, uncommon sense) are important in science. Horgan has staked an extreme position that seems indefensible on these grounds, but makes approximately the right broad claim. However, this broad claim then undermines his more specific argument against string theory, that it’s untestable. (For an example of a theory that philosophical concerns should drive us against, despite its empirical adequacy, see here.)

In other news, I’m leaving for Sydney airport in a few hours, and then will be on a roadtrip through Arizona and New Mexico for about a week or so before returning to Berkeley, so I’m unlikely to post until the end of the month.




7 responses

19 08 2005
The Cardinal Collective

Horgan on Common Sense

I’ve got a post at Antimeta that non-philosophers might be interested in. I discuss some debate about string theory, and also point out that I won’t be posting here or there for about a week and a half….

22 08 2005

Is the position of string theory really any different from that of Newton’s laws of motion? Newton posited some ideal rules of operation, applicable to idealized objects operating in circumstances abstracted away from reality. By their very nature, such rules of operation were not falsifiable, since there were never any real circumstances or objects which matched their pre-conditions.

Yet we accepted them as “true” (or at least, as “good enough”) descriptions of reality for nearly 250 years. One reason we did so is because they are elegant. The same is said to be true of string theory, to those who know its mathematics.

23 08 2005

I think that the position of Newtonian mechanics and string theory is fairly similar, but not for the reason you cite. If they’re considered merely as mathematical theories, then of course they’re both fine (that is, neither seems to be contradictory, and both have models in ZFC), but that’s not really the interest of these theories. Rather, both seek to describe the real world, at least approximately. To “falsify” them would be to show that most real-world bodies behave in ways that aren’t usefully approximated by the laws, or are better approximated by some other theory. Thus, Newtonian mechanics was falsified by relativity. If I’m right about string theory making approximately the same predictions as the current combination of quantum mechanics and relativity (and I may well be wrong about this), then we would either need to falsify current theory, or find some theory better than both in order to falsify string theory. Or possibly do some detailed experiments to get evidence that the minor differences between current theory and string theory favor one over the other.

But of course, since both are approximate descriptions of reality, and both seem pretty decent, they’ll stick around even after falsification as interesting mathematical systems, both because of their elegance and because of their usefulness, even though we won’t regard their applied versions as true any more.

26 08 2005

Topological quantum field theory is certainly good maths, since it can be used to give invariants of manifolds, which may help in classification programs (or may already have, I don’t know, not my area).

27 08 2005
d t locke

I came here because of your comment on my Azzouni post. I’m excited to see that you’ve been reading and posting on Deflating Existential Consequence. When I get a chance, I’ll be reading through your posts and I’ll hopefully have something we can talk about. I look forward to it.

31 08 2005

Kenny —

“To “falsify” them would be to show that most real-world bodies behave in ways that aren’t usefully approximated by the laws, or are better approximated by some other theory.”

I have to take issue with this statement of yours. I think your definition of “falsify” here is not at all the one which most scientists and most philosophers of science would use. I have three objections:

1. You say “most real-world bodies”. But Newton’s theory (as all subsequent theories in the same domain) purports to be about “all” bodies, not “most”, of a certain class. Only one exception in the specific class of objects is needed to falsify such a theory. (As I state, Newton’s theories were not about real-world bodies, but idealizations of them — perfectly spherical planets, with uniform mass distribution, etc.)

2. You say “aren’t usefully approximated”. This introduces a pragmatic element, which I doubt any scientist would consider appropriate in a search after truth. Falsification is about testing the truthfulness of representations of reality, not about the usefulness or value of a representation. Indeed, the Catholic Church in supressing Galileo accepted that his theories were more likely “true” than were the prior theories, but believed that dissemination of such theories would be socially disruptive; his work was suppressed on pragmatic grounds.

3. “or are better approximated by some other theory”. But falsification of Theory X does not require, in most people’s views of the word “falsify”, a prior statement of an alternative Theory Y. What you are talking about here (I think) is choice between competing theories, which is not the same process at all as falsification of a single theory.

So, I repeat my original claim: Newton’s laws of motion were not falsifiable, since they do not describe real-world entities or circumstances. (To be fair, Newton did not ever purport that they did.) All one could do with them was to assess whether or not they were useful, for particular purposes.

Moreover, following your post, I further claim: Newton’s laws were not falsified by Einstein’s theories; rather Einstein’s theories were applicable to a broader class of objects and circumstances than were Newton’s, and the entities in this broader class, although still idealizations, were closer to those observable in the real-world than the ideal objects and circumstances to which Newton’s laws applied.

Apologies if you think this pedantry, but pedantry is in fact how science (particularly mathematical science) progresses.

2 09 2005

I agree that pedantry (of the appropriate sort) is important and useful.

The reason I added the three sets of weasel words that you object to is precisely in order to make it plausible that people actually accepted Newton’s laws, and they didn’t come into existence already falsified.

I said “aren’t usefully approximated” in order to allow Newtonian mechanics not to be falsified by experiments (that may or may not have interference) that differ subtly from the predicted motions. It’s probably right that one doesn’t always need a better theory in order to falsify the previous one, but note that it was several decades between the Michelson-Morley experiment and the rejection of Newton/Maxwell dynamics. Kuhn points out many other examples, which I think were appropriate positions in the history of science, where people held on to theories after they were “falsified” in a weak sense but before a better theory came along.

The “most” in “most real-world bodies” might have been a bit of a slip, but if we discovered some strange, extremely rare type of object that didn’t obey Newtonian laws, we would just slightly modify Newton’s laws rather than saying they’re just plain wrong. True, we’re rejecting the literal statement of the previous theory, but in such a minor way that it seems wrong to say we’ve “falsified” it.

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