The first weird and manifestly pathological feature of these obsessed anti-string activists is that for years, many of them (especially the "leaders" of the movement) have been saying that string theory was untestable. Quite suddenly, it was tested and "blown out of the water". Holy cow. If you can't falsify a theory, how can you suddenly falsify the theory? The IQ of the individuals who are unable to notice this basic inconsistency must be closer to the IQ of an average chimp than to the IQ of an average human.
Strassler repeats all the basic observations that have been explained hundreds of times on this blog and elsewhere. It's my guess that it won't change anything. He says that string theory is being connected with the world of phenomena at least in two ways – as a unifying quantum theory of gravity and other forces (and matter), something that real string theorists actually find important; and as a mere tool to produce new calculational techniques for the strong nuclear force etc. (something he has worked on).
The anti-string critics are mixing these things all the time. They also confuse a prediction that may be tested in principle (and string theory is full of those; and this is what makes it indisputable that it is a scientific enterprise) with a prediction that may be tested in a particular experiment of a foreseeable future. String theory as a unifying theory is of course a long-term goal, a new framework for theoretical physics that's here to stay for decades or a century or permanently, so of course that some particular excitement with an experiment that is performed on Friday morning or in 2012 isn't the primary determinant of string theory's fate – and it has never been.
Matt Strassler also distinguishes the predictions of particular string vacua from the predictions of the whole string theory framework. He argues – like your humble correspondent and dozens of people before us – that from a practical perspective, the predictive power of string theory as a framework is about the same as the predictive power of quantum field theory as a framework. In the most general form, you could say that neither of them predicts "anything" we can really observe (it's not really true but let me not go into that); a specific model (a string theory vacuum or a particular QFT) predicts pretty much everything – another question is whether we are able to calculate the predictions.
So any suggestion that string theory is in a worse shape than quantum field theory when it comes to real-world predictions is simply untrue. String theory only reparameterizes the space of possible theories or environments differently. Instead of the low-energy spectrum and the low-energy values of some coupling constants, string theory classifies the possibilities according to the high-energy behavior of the degrees of freedom in physics, qualitative properties of the compactification of the extra dimensions and other properties that may only be "directly measured" using in practice inaccessible very high-energy probes.
In reality, when you look at the big picture, the status of string theory is of course better than the status of quantum field theory. It is more predictive because the number of stabilized string vacua is countable (i.e. discrete) and, when basic constraints are imposed, probably finite. This makes string theory more predictive than quantum field theory, at least in principle. Also, all the "different string vacua" are actually connected – they are solutions to the same stringy equations. This situation is contrasted with the situation in quantum field theory where different quantum field theories are completely disconnected. Finally, string theory is more well-behaved (well, completely well-behaved) at very short distances which is particularly important for gravity (whose Planck-scale behavior can't be described by a quantum field theory in the spacetime at all) but not only for gravity.
I find these exchanges tiresome because they have taken place so many times and nothing has come out of them. If someone needs more than half an hour to absorb and verify (using other sources or his own thinking) the five basic paragraphs about the predictivity and basic status of string theory above – or if he's even willing to remain confused or ambiguous about them for years – it's just a waste of time to write dozens or hundreds of comments for that person. He will never get it. He is too intellectually limited. He will always be inclined to read tirades by anti-string conspiracy theorists and prolific crackpots.
But there are proclamations by Matt Strassler I disagree with, too. One of them is his "agnosticism" about whether "useful, immediately usable predictions" are needed for a theory to be scientific. It is not a matter of personal preferences. Science simply doesn't depend on any "fast applications"; applications of science are completely different entities than science itself. Even things that have no imaginable or foreseeable applications are scientific if they have in principle observable consequences and empirically rooted evidence backing them. However, this disagreement is far from being the only one. Consider this quote:
The string theorists over-sold their theory; [Voits] is underselling it; don’t listen to either of them, just think carefully and listen to sensible people without an axe to grind.I have restored the actual name of one of the activists (one of the two most notorious ones, in fact); like many families who flew to Latin America after the World War II, he is distorting his last name in order to hide that his ancestors were largely (at least among the locals) responsible for the murder of 40,000 Jews in Riga in 1941, a history that he finds inconvenient now when he decided that his well-being depends on his being an extreme leftist.
Fine. Let's look at Strassler's comment.
There have surely been people who "oversold" something. When Michio Kaku or even Brian Greene were explicitly or at least implicitly promising you time machines that will produced because of advances in string theory, they oversold the practical power of string theory. When someone would "promise" that it's guaranteed that an experiment that has already been performed would have to observe some beyond-the-Standard-Model physics, they surely oversold the "urgency" of string-theoretical predictions as well – simply because no BSM physics has been observed yet.
However, when Edward Witten "guessed" that the single right string theory compactification capable of predicting all particles' properties would be found within weeks back in 1985, it was just a guess that turned out to be overly optimistic but that reflected this top scientist's best judgement at the moment. There were very good reasons to think so. But he would never claim that this expectation had actually been established.
On the other hand, as Edward Witten pointed out a few years ago, even (most) string theorists underestimate the actual richness and strength of string theory. I completely agree with that and I would present this thesis as a self-criticism, too. Even if you read The Reference Frame, you will be led to think that string theory is less rich, important, and powerful than it actually is.
Even more importantly, I completely disagree with Strassler's statement that "you should listen to the people in between". If you want to become a brainwashed moron, you should listen to the anti-string demagogues. If you want to become something in between a brainwashed moron and a well-informed interested layman, you should listen to the people who are somewhere in between the experts and the anti-string demagogues (although I do admit that Matt was closer to the experts in this particular exchange).
But if you actually want to accurately learn how the theory works, what it says, what it has demonstrated, and what it hasn't, you don't have a choice: you have to listen to the actual experts and not just semi-experts like Matt Strassler.
Try to think about it. It's completely obvious. But politically correct attitudes of people who are "always somewhere in between" have penetrated deeply to the psyche of the society. The PC-inspired misunderstanding of the process to find the truth is so deep and widespread that even the statement that "you are likely to get the more accurate information about a theory from an expert than from a bystander" has become controversial. If you evaluate whatever information you're able to evaluate and conclude that all the claims that "string theory remarkably and nontrivially works" are lies, you should just ignore string theory (and vote against it in all funding and hiring decisions you are expected to influence) because it doesn't have any value according to your views and the whole "community" is just deluded. But if you're able to figure out that this conclusion is an indefensible conspiracy theory and there's quite a body of evidence and a mathematical structure that some people have partially or largely mastered, experts are the only folks who can really teach you things at the expert level.
This observation of mine isn't just a truth in principle. It takes on a real shape in every discussion of this kind. For example, Joseph Conlon, a string phenomenologist from Oxford, joined the discussion and corrected Matt Strassler's inaccurate claims that a theory like string theory can never predict general things about physics at much-lower-than-the-fundamental scale. For example, the predictions of an axiverse – a large number of axions with hierarchical masses at many scales – is implied by certain classes of the string vacua. These axions are hard to observe – but not because they're heavy; it's because they are weakly interacting with the known particles.
So what Matt Strassler wrote about all these technical things is just wrong. Such wrong things written by "people in the middle" are often tolerated and people tend to absorb them because we live in the society where mediocrity largely rules. But they're as wrong as some of the technical claims made by the hardcore anti-string conspiracy theorists. Matt Strassler and people "who always want to be in the middle of the society, as a matter of principle" never become the main targets of a criticism in any polarized debate. Why? Simply because in a polarized debate, only a "sign" or "magnitude" or someone's positions along a one-dimensional axis is what matters to many folks. Because Matt Strassler and similar folks are never viewed as "extreme ones", the people who care about the signs only just don't attack them.
Your humble correspondent doesn't approach the situation in this way. The whole "polarization" of a discussion is an artifact of the participation of the stupid and dishonest people in the discussion. If Voits and others were consistently treated as what they are – obsessed, loud, deluded, and dishonest crackpots – we would never try to project statements on a "one-dimensional, string/anti-string political axis". And I am never projecting statements on an axis. I am evaluating the validity of statements by carefully looking at the evidence. And many of the technical statements of Matt Strassler about string theory are just wrong which is not shocking because he's not a real expert.
Of course, he's still way closer to being a string phenomenology or string theory expert than (with a few exceptions) the folks who opposed him in this particular exchange.