For moral realism to be true in the sense which most people mean when they talk about it, “good” would have to have an observer-independent meaning. That is, it would have to not only be the case that you personally feel that it means some particular thing, but also that people who feel it to mean some other thing are objectively mistaken, for reasons that exist outside of your personal judgement of what is or isn’t good.
That would only be a case of ambiguity (one word used with two different meanings). If you mean with saying “good” the same as people usually mean with “chair”, this doesn’t imply anti-realism, just likely misunderstandings.
Assume you are a realist about rocks, but call them trees. That wouldn’t be a contradiction. Realism has nothing to do with “observer-independent meaning”.
For a belief to pay rent, it should not only predict some set of sensory experiences but predict a different set of sensory experiences than would a model not including it.
This doesn’t make sense. A model doesn’t have beliefs, and if there is no belief, there is nothing it (the belief) predicts. Instead, for a belief to “pay rent” it is necessary and sufficient that it makes different predictions than believing its negation.
If you call increasing-welfare “good” and I call honoring-ancestors “good”, our models do not make different predictions about what will happen, only about which things should be assigned the label “good”. That is what it means for a belief to not pay rent.
Compare:
If you call a boulder a “tree” and I call a plant with a woody trunk a “tree”, our models do not make different predictions about what will happen, only about which things should be assigned the label “tree”. That is what it means for a belief to not pay rent.
Of course our beliefs pay rent here, they just pay different rent. If we both express our beliefs with “There is a tree behind the house” then we have just two different beliefs, because we expect different experiences. Which has nothing to do with anti-realism about trees.
That would only be a case of ambiguity (one word used with two different meanings). If you mean with saying “good” the same as people usually mean with “chair”, this doesn’t imply anti-realism, just likely misunderstandings.
Assume you are a realist about rocks, but call them trees. That wouldn’t be a contradiction. Realism has nothing to do with “observer-independent meaning”.
This doesn’t make sense. A model doesn’t have beliefs, and if there is no belief, there is nothing it (the belief) predicts. Instead, for a belief to “pay rent” it is necessary and sufficient that it makes different predictions than believing its negation.
Compare:
If you call a boulder a “tree” and I call a plant with a woody trunk a “tree”, our models do not make different predictions about what will happen, only about which things should be assigned the label “tree”. That is what it means for a belief to not pay rent.
Of course our beliefs pay rent here, they just pay different rent. If we both express our beliefs with “There is a tree behind the house” then we have just two different beliefs, because we expect different experiences. Which has nothing to do with anti-realism about trees.