[Serious] An Argument Against Hedonistic Moral Realism

[The Grand Nudger]

The mind independence that ethical theorists are discussing literally -is- what you're calling independence of opinion.  Mind independence, of this sort, is the central contention of realism.  Your premise two is "the only way realism can be true, is if moral realism is true".

To riff off of Boru, while it may not be immediately obvious that moral realism is true, that moral x's are mind independent, it is immediately obvious, at least, that for moral realism to be true, moral realism must be true.  

Both realists and subjectivists, people who think that moral x's are mind independent, and mind dependent..respectively, accept that pleasure and pain come from our minds.

-enjoy

Second, it is not clear that maintaining the “mind-independence” clause as a defining feature of the realism/anti-realism division really does make psychological realism a “non-starter.” Perhaps all that is needed is a more careful understanding of the type of independence relation in question. Certainly there is a trivial sense in which the truth or falsity of a psychological claim like “Mary believes that p” depends on a mental fact: whether Mary does believe that p. On the other hand, there is also a sense in which whether Mary has this belief is a mind-independent affair: The fact of Mary's believing that p is not constituted or determined by any of our practices of judging that she does so believe. We could all judge that Mary believes that p and be mistaken. Most people would accept that even Mary might be mistaken about this—erroneously judging herself to believe that p. In the same way, although the moral claim “Mary's action was morally wrong” may be true only in virtue of the pain that Mary's action caused (or because of Mary's wicked intentions), this may not be the right kind of mind-dependence to satisfy the non-objectivist clause.

https://plato.stanford.edu/entries/moral-anti-realism/

b-mine