Indeed.
Here's the thing. Either we can come up with an experiment to distinguish materialism from idealism, or the distinction will be based solely on axiomatic assumptions. If the latter, there will be no proof, because axioms are ... well ... axiomatic.
However, there is one thing I bet we could prove: that the two sets of axioms are equivalent.
Exactly. I don't see the point of all the intellectual contortions.
You pick up a ball. It is either "real" or "not real" whatever that means.
You drop the ball (or you perceive yourself dropping the ball, remember, I'm not suggesting that this ball has an independent objective existence).
What do you perceive now? Do you see a ball falling? If it is heavy and lands on your foot does it hurt?
If you have another ball, which you perceive to be pretty much identical to the first, and you drop them at the same time, will you perceive them to land at the same time?
Are the relationships between the things that we perceive consistent? Are we able to model those relationships with "physical laws"? Again, I'm not suggesting that those physical laws tell us anything about "reality", I'm just saying, do they accurately model what we perceive?
Or is our thought able to alter those perceived relationships?
If not, does it matter if we call those things real or not? What does it mean, anyway, if they aren't?