I just read a horrifying article in Nature. The article, Scientific method: Defend the integrity of physics, recounts an effort among some theoretical physicists to redefine the scientific method so that it no longer requires experimental verification or even that a theory needs to be testable in principle.
The issue is that much of string theory, an entirely theoretical construct, is not testable, even in principle. It has been widely criticized on those grounds. The string theorists are now arguing that it should be enough that a theory be “elegant” and that philosophical and probabilistic arguments should suffice.
What could go wrong? Even a meager imagination can dream up plenty of ways that such a move could end in disaster. An easy example: an elegant, untested, and untestable theory predicts that global warming is (or is not) a threat and we take an action (exploding the world economy or ignoring the threat) based on that theory that turns out to be wrong1. Would you trust a politician or vested interests with such a theory. Experimental verification is required precisely because it gives us confidence that a given theory is true.
Whatever you think about logical positivism, it seems to me that it’s correct in its tenet that ideas or theories that can’t be verified or falsified, at least in principle, are meaningless. If I announced to the world that magical beings inhabit our world but that you can never prove their existence or nonexistence, I’d be widely ridiculed as delusional. I might even come up with some mathematics that’s consistent with the existence of such beings. I’d still be ridiculed.
To me, the issue is clear. If you tell me that your theory isn’t testable, I’ll tell you it’s not science.
Footnotes:
Save your stamps. This is an entirely hypothetical example and says nothing about whether or not global warming is a threat.