There are similar issues with Penrose’s claim that fashion is the main reason for string theory’s influential position. His analysis of its problems is not up to the task of debunking proponents’ physics-based reasons for confidence. Penrose’s main complaint about string theory is that it lacks a clear specification of its number of degrees of freedom. He tries to show this in several contexts. However, he tends to omit information that could make the situation less confusing than he takes it to be. For example, he expresses unease about ‘gauge–gravity duality’, the claim that string theory is empirically equivalent to a quantum field theory in a lower-dimensional space. (If generally valid, that would mean that a string theory in three extended spatial dimensions was empirically equivalent to a quantum field theory in two spatial dimensions.) Such a claim looks startling, because one would naively expect that a three-dimensional theory has more degrees of freedom than a two-dimensional one. Penrose presents this as one of many questionable implications of string theory. More.
Rob Sheldon retorts:
I have the greatest respect for Roger Penrose. Despite being a member of the British Humanist Association, he is an old-school atheist, of the sort that Sir Fred Hoyle and Anthony Flew belonged to. This is to be separated from the new, angry atheist epitomized by Richard Dawkins.
So when Penrose writes a new book entitled “Fashion Faith and Fantasy in the New Physics of the Universe”, he isn’t just channeling Denyse’s blog posting*, but he expressing as calmly as only a rational Brit can, that theoretical physics has gone off the rails.
Alas, who do they get to review his book? Richard Dawid, they guy who so wants string-theory to be true that he says experiment is no longer required. So naturally when Penrose is ripping into string theory, Dawid takes offense. Here’s Dawid,
There are similar issues with Penrose’s claim that fashion is the main reason for string theory’s influential position. His analysis of its problems is not up to the task of debunking proponents’ physics-based reasons for confidence.
Wow. So Dawid’s aesthetic judgment that string theory is true because (as Peter Woit documents,
The currently predominant philosophical conception of theory confirmation (Bayesianism) equates confirmation with the increase of the probability that a theory is true or viable. For that reason I speak of “non-empirical theory confirmation.”
But more importantly for our discussion, the arguments for the viability of string theory are based on meta-level observations about the research process. As described before, one argument uses the observation that no-one has found a good alternative to string theory. Another one uses the observation that theories without alternatives tended to be viable in the
Ergo, Roger Penrose’s alternative to string theory shows he isn’t “up to the task” because string theory has no rivals.
Poor Dawid. Poor Penrose. If human rationality is our god, then we will all be sacrificed on the altar of human irrationality.
*Note: Penrose is more likely to be channelling cosmologist George Ellis’s concerns, as expressed in Nature, than News’s (Denyse O’Leary).
See also: Breaking: Article in Nature defends integrity of physics against multiverse, string theory
Peter Woit contemplates the end of physics
The bill arrives for cosmology’s free lunch
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