Structures with predictable behavior - eg drugs that will alleviate suffering, chips that will compute, etc. I take no position on whether it's ok to ignore philosopy, but as far as I can see they largely do. It doesn't matter to me whether logical positivism is correct - I'm saying people doing science clearly seek predictive knowledge. Models are predictive. If you still disagree, I'm not sure we can come to any agreement here.
> The chemists methods were (typically) scientific and rational, even though they did not reach a good understanding of chemistry using these methods for quite some time.
They're only "scientific" & "rational" in retrospect because you now know what is actually happening. When solving chemical equations, you must take into account atomic numbers, which they did long before knowing about atoms. There's no a priori reason why certain compounds must always be in certain proportions. All they knew is it worked well.
> Certainly, if our brains were different we might have different moral beliefs, but that does not imply that those beliefs would be equally correct.
So if our current brain structure is an accident of evolution what makes our present moral beliefs more correct? Geometry has real world consequences that don't change if brain structure changes. Coincidentally the only moral facts that aren't already changing (much) are those crucial in evolution.
> I am curious, though, why you are so sure that moral facts must be reducible to physical facts.
It's inconcievable to me how you can make a statement about this reality without (eventually) referring to some observation/experiment -- ie some test that argues for that outcome over other possible outcomes. If you claim moral beliefs aren't based on reality then clearly they're arbitrary.