What can science prove?

[Tiberius]

Science says the things I can see exist.

Reality check #1.

Science does not say that. Science assumes it (as surely it must). It might be helpful to consider the word "says" (in this context) as idiomatic, that is, 'what science says' is an idiom whose literal meaning is 'what science concludes'. The things you can see exist, yes. But that is not a conclusion reached through scientific methodology; in fact, the issue is not even available for empirical review in the first place. What exists? What does it mean for something to exist? When does something cease to exist? This is philosophy, not science. The branch of philosophy known as metaphysics is where conclusions are drawn about ontology (existence). Science does not, and cannot, draw those conclusions. It assumes them.

I think you are perhaps over-analysing what I said. Science does make this conclusion, as it involves the reflection of light off objects into my eye. Science further says that things I can hear (i.e. producing soundwaves that get picked up by my ear) exist. I wasn't making some sort of metaphysical claim here, only that science tells us the things we see are real because we understand through science how we see them.

Further, I cannot see how you can reconcile this with what you say below, that "material things do exist". If material things do exist, and light is material, then we can make the conclusion that things light interacts with also exist.

Science relies on the assumption of materialism.

Reality check #2.

Science does not rely on that assumption. Insofar as science is occupied with the study of natural causes and events, it assumes that material things exist (as noted above) but it does not assume that ONLY material things exist. You are conflating an epistemological assumption (which science relies on) and an ontological assumption (which science does not rely on), the latter being the presupposition that "nature is all there is, and all basic truths are truths of nature" (The Encyclopedia of Philosophy. Macmillan, 1996). Even if metaphysical naturalism were shown to be complete bollocks, we would still have the natural sciences because material things do exist.

If metaphysical naturalism were untrue, then yes, we would still have the natural sciences, but we would have to change them radically, as I noted. What if the reason gravity exists is because of some supernatural gravity being? What if the tides were controlled by spiritual beings?

The reason science currently does not look into such possibilities is because it is working within the confines of naturalism. It assumes naturalism in order to process information about the material world we know exists (as you admit).

If naturalism is untrue, science as we know it will have to re-evaluate everything it has deduced. You can still rebuild science out of it, but the refutation of naturalism would kill science as it stands today.