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.