Some predictions string theory may give cannot be calculated. It’s not accessible by present-day experiments or experiments in the foreseeable future. So what can we do with a theory of that kind? We don’t want to live with a theory for 50 years and have no clue whether it’s viable or not.
You would think this would be an issue. One might think that it would bother people that string theory has a lot of things that cannot be calculated.
You would think it would bother more people that there is no known practical way to test string theory.
And it does bother some people. It bothers people that string theory gives values of infinity for things like the properties of objects. But it does not bother people as much as it should.
A theory that does not even allow things to be calculated, let alone tested, sounds problematic to me. Is it even a theory at this point?
Some people try to rationalize the infinities away or come up with ad-hoc methods to get finite values. Or just pretend that one day string theory might be testable.
One day in a faraway land, huh? Sure, sure…
Richard Dawid then proceeds to identify three reasons why he thinks people accept string theory.
The first is what he calls the no-alternative argument.
That is, string theory is the only seemingly plausible theory anyone has found.
Is it plausible though? I would argue that it is not. It relies on a lot of nonsense like reification of the concept of dimension. And “one-dimensional” objects called strings.
But, even if string theory was plausible, the fact that it is plausible is no reason not to seek evidence to test it.
I could probably, given enough time, come up with a plausible theory of gravity in my head. That is, I could come up with a theory that might seem to be consistent with observable facts.
But does that mean that I should assume that it is true? Should I assume it is a valid explanation of physical objects and the interactions between them we refer to as gravity?
No. I still need to verify that this proposed explanation concords with reality. I still need to show that yes, my explanation is how this works.
The fact that you or I might not be able to think of an alternative theory does not justify blindly assuming my current theory is true. And this is the case with string theory.
Then he offers the meta-inductive argument.
This claims that if a research program has come up with a good theory in the past, later theories are assumed to have a higher chance of being right.
That is a rather silly assumption. Just because I am right about some other thing is not a reason to blindly assume that I am about this other thing.
Yes, if I have a track record of good science, one has a reason to be more confident that this theory might one day be shown to be right. But the theory still needs to be tested like any other. I have no reason to assume it is true in the absence of evidence.
And thirdly, he offers the unexpected coherence argument.
This is where a theory solves physics questions beyond those it was intended to. As though the fact that it has applications other than those initially predicted somehow proves that the theory is true.
But just because I might be able to use the theory in unexpected ways, if it is true, does not prove the theory is true. I still must establish that it is true.
Even taken together, these arguments are not as strong as empirical evidence, Dawid notes. But they are better than other reasons physicists might put forward for supporting a certain model, such as whether or not a theory is beautiful.
They certainly are not as strong as empirical evidence. Perhaps they are better than some other reasons given for accepting models. They are perhaps better than “it is true because the math is pretty”. But even if they are better, that has no bearing on whether they are true!
Sorry Dawid, you have failed to provide any reasons why we should take string theory seriously as physics. Hardly surprising really. Given you do not seem to understand what science is or how it works, despite being a philosopher of science.