String Theory vs the Popperazzi

There is trouble in the fundamental physics community. Can philosophers help?

There is trouble within the fundamental physics community, as the title of a popular book by physicist Lee Smolin openly puts it. The trouble in question is rooted in the dominance of so-called superstring theory, despite its utter lack of empirical verifiability (as Peter Woit, another critic, put it in the title of his book, it is “not even wrong”).

Not so, replies prominent physicist Leonard Susskind in yet another book written for the broader public, accusing colleagues like Smolin of being “Popperazzi,” i.e., rather unthinking followers of the philosopher Karl Popper and his idea that scientific theories ought to be falsifiable (i.e., capable of being shown false on empirical grounds, if they are, in fact, false).

What’s going on here? Welcome to the Physics Wars (TM). Smolin and Susskind are far from the only highly visible players in the physics community to make uncharacteristically, shall we say, bold statements about each other’s credentials, intelligence, and more or less base (as seen from the other side) motives.

When George Ellis and Joe Silk wrote an op-ed in the prestigious Nature magazine, dramatically entitled “Defend the integrity of physics,” cosmologist Sean Carroll responded via Twitter (not exactly a prestigious scientific journal, but much more effective in public discourse) with, and I quote: “My real problem with the falsifiability police is: we don’t get to demand ahead of time what kind of theory correctly describes the world.” The “falsifiability police”? Wow.

This is actually all very amusing from the point of view of a philosopher of science. You see, our trade is often openly despised by physicists (the list of offenders is long: Steven Weinberg, Stephen Hawking, Lawrence Krauss, Neil deGrasse Tyson — see for instance this, or this), on the grounds that we are not useful to practicing scientists.

But here we are, the scientists are having a very public squabble about the foundations of their field, and they either eagerly invoke (Smolin, Ellis, Silk, and others) or vehemently reject (Susskind, Carroll, and others) what a prominent philosopher of science wrote a number of decades ago about the nature of science!

The focus, of course, is superstring theory and related concepts (such as that of a multiverse), which appear to be dominant in the fundamental physics and cosmology communities at the moment, and yet have gathered an increasingly vociferous number of critics who allege that these mathematical constructs are just that: math (possibly even useful math), but not science.

Which means that the issue is one of demarcation between science and non-science, a notoriously difficult one, and precisely what prompted Popper to put forth his (in)famous criterion of falsifiability in the first place.

The naive version of that proposal (which is not clear whether Popper ever held, while it is clear that he did not hold it later on in his career) amounts to say that for a theory or hypothesis to count as “scientific” it ought to be falsifiable in principle. To use Popper’s own original examples, general relativity is in, various versions of psychoanalysis and Marxist accounts of history are out. The reason is that general relativity has withstood “risky” tests that it could have easily failed (like the famous measurement of a small degree of bending of the light by the Sun during the 1919 total eclipse), while psychoanalysis and Marxism can accommodate pretty much any new fact because they are so inherently flexible that they are “compatible” with anything that gets thrown their way.

The problem with current accusations of “Popperazzi” and “falsifiability police” is that there is a significant amount of damage that can be done by a little (but insufficient) knowledge, in this case, physicists’ knowledge of philosophy of science.

You see, Popper and falsificationism are two of the few names and concepts any scientist is likely to have heard of from philosophy of science (two more are Thomas Kuhn and paradigm shift). But having heard of something isn’t the same as being knowledgable about it — in the same way that I’ve heard of string theory, but I most certainly wouldn’t know what I was talking about if I had to give a professional opinion about it.

Not only the physicists in question do not seem aware of the fact that Popper’s own ideas about falsifiability evolved significantly over the many decades during which he was active as a philosopher. They also seem to think that philosophy of science ground to a halt back in the 1960s, which it manifestly didn’t.

Modern philosophers of science always pay due homage to Popper (and his often underestimated student, Imre Lakatos; and to Kuhn; and to Paul Feyerabend; and to a few others from that glorious period), but they then go on to discuss a number of more recent and more sophisticated treatments of the nature of the scientific enterprise — like those based on Bayes’ theorem, for instance. Of course, nobody expects physicists to be up to date on philosophy of science, since it isn’t their technical field of expertise. But there is something deliciously ironic about the Physics Wars (TM), where both sides attempt to enlist philosophy’s helps in the furthering of their agendas. And, predictably, get it largely wrong.

So, what should a savvy physicist do in these cases? Just give up and ask the philosophers whether superstring theory is science or mathematically informed metaphysics? That won’t do. For one, because the scientists are simply never going to cede epistemic authority to outsiders — nor should they. But also, there is interesting disagreement among philosophers themselves on this matter. For instance, Richard Dawid, a philosopher at the Munich Center for Mathematical Philosophy, has argued in favor of embracing what he terms “non-empirical confirmation,” where the value of a theory is judged in conjunction with empirical confirmation elsewhere in the same field, assuming that a long term perspective of empirical confirmation exists for the given theory (which, of course, it is very much debated in the cases of string theory and the multiverse). This is far from an uncontroversial take on theory confirmation, and it remains to be seen how the rest of the philosophical community will react to it.

A better course of action would be to get both scientists and philosophers to seat at the high table and engage in constructive dialogue, each bringing their own perspective and expertise to the matter at hand. It would be helpful, however, is this happened with a bit less mud slinging and a bit more reciprocal intellectual respect. But perhaps that’s asking too much, given the prestige and level of funding commanded by whoever will win the Physics Wars (TM). Even physicists, after all, are human beings.

Note: this is an updated version of the original essay, which corrects a mischaracterization of the ideas of Richard Dawid. I wish to thank him for having drawn attention to my misperception.

MASSIMO PIGLIUCCI IS THE K.D. IRANI PROFESSOR OF PHILOSOPHY AT THE CITY COLLEGE OF NEW YORK. HIS BACKGROUND IS IN EVOLUTIONARY BIOLOGY AND THE PHILOSOPHY OF SCIENCE, THOUGH HE HAS RECENTLY DEVELOPED A KEEN INTEREST IN STOICISM. HIS MOST RECENT BOOK (CO-EDITED WITH MAARTEN BOUDRY) IS “PHILOSOPHY OF PSEUDOSCIENCE: RECONSIDERING THE DEMARCATION PROBLEM” (UNIVERSITY OF CHICAGO PRESS, 2013). HIS OTHER WRITINGS CAN BE FOUND AT PLATOFOOTNOTE.ORG.