Non-reductionism About Semantics
There is no reductive connection between moral terms and concepts and natural terms and concepts. This gives Cornell realists a simple response to the charge that you cannot have naturalism without naturalistic fallacy: namely, that metaphysical reduction doesn't imply semantic reduction. This usually goes with a Kripke-Putnam semantic story: moral terms and concepts pick out certain natural properties in virtue of those properties standing in an appropriate causal (social-historical) relation to our tokenings of the terms and concepts.
Read more about this topic: Cornell Realism