> What does that mean? And how can math be so useful in physics if it has nothing to do with reality? [1]
I encourage you then to read mathematicians and physicists rather than philosophers. Math is basically a self-consistent formal language for describing ideas. With a language you can express all sorts of ideas that aren't actually physically possible. Physics is the exploration of which mathematical ideas can be used to describe observed reality. Math is useful precisely because it is formal and self-consistent. You can verify if the math is correct before you start building experiments to test if reality conforms to a given idea. For example, while we know black hole's exist, physicists generally acknowledge that our understanding of the interior are unlikely to be accurate because our current mathematical equations spit out infinities for the interior.
> Excuse me? According to whom? This is preposterously false. The claim you are making is a philosophical one, and an extremely naive one, and I invite you to study the philosophical analysis of that claim
Logic, math and the scientific method came out of philosophy. Philosophies contributions basically end there as far as I'm concerned. Philosophy continued to dick around with empirical approaches to logic and gave up in the 17th century until mathematicians revived it using formal methods and proofs. It poses hypothetical problems as if they're unanswerable only for science and mathematics to come by and render them obsolete (from Xeno's paradox which is answered by infinite sums to the trolly problem which is answered by "the answer is to avoid such artificial constructions at all costs rather than know how you behave in that scenario" which is also how we've trained AI to operate as well).
> Thomas Nagel, for example, is known for his criticisms of physicalism
Right. It's pretty expected for religious people to have a problem with physicalism because it's pretty atheistic in nature. The underlying philosophy of the scientific method is "everything that's physical follows the rules of physics and we can explore it, test it, observe it and understand it while everything else is not science". Religious people have a problem with this because it clearly separates God and science and they try to reinject God by trying to falsely equate physicalism and religion as the same thing.
> Bertrand Russell also had some things to say about the nature of physics that you might find interesting
I have no qualm with Bertrand Russell. He's a brilliant thinker and I agree with his critiques which aren't a refutation but a clarification that we can know the structure of the physical world (as expressed in equations and laws) but not necessarily the intrinsic nature of its entities.
I think a lot of scientists, physicists agree with this insofar as "intrinsic" by its definition is unknowable. There's an alternate branch of thought which says "reality is what the math says". The beauty of this is it's a metaphysical unknowable argument like religion and thus which side is right or wrong is completely unknowable and outside the real of science.
Russell saw physics and philosophy as mutually reinforcing. He believed that philosophy must take into account the best scientific knowledge, but also that science rests on philosophical foundations (like logic, mathematics, and epistemology). The problem I have is that while it does, the philosophical foundations are unchanging and not what people think of as "modern philosophy" which is just rehashing all the same old tired arguments and not actually coming up with ideas on how to solve them (which is what something like Xenox's paradox was). The "true" philosophy of "here's a problem we don't know how to solve" remains in the realm of physics (e.g. the open problems about gravity & quantum, the origin of the universe, etc)