Realism about scientific theories and realism about normative moral propositions each begin with a semantic thesis: there are true statements in the category in question and the true ones are true independently of whether anyone thinks they are true, and also are true independently of whether anyone would come to believe them if they thought about the question in a certain way. There are two declarations of independence here.
The two realisms I want to discuss here defend the semantic theses just mentioned in an indirect way. They don’t directly address the class of all scientific theories or the class of all moral statements, but rather single out special subsets of each. We have good reason to think that certain scientific theories are true because the hypothesis that they are true provides the best explanation for why those theories accurately predict what we have observed. And we likewise have good reason to think that certain normative moral statements are true because those statements provide the best explanations of some of the (non-normative) observations we have made.
Two Cornell Realisms ─ Moral and Scientific
by Elliott Sober
https://827166e3-a-bf4ca052-s-sites.googlegroups.com/a/wisc.edu/sober/selected-papers/PS-2013-TwoCornellRealisms.pdf
Elliott Sober
http://sober.philosophy.wisc.edu/home