As for common language, I think what HM means is that a “realist” is usually someone who denies the existence of things, such as fairies. When people in international relations hold a realist) stance, they aren’t saying that they believe in something that their opponents don’t (as philosophers would), but that they believe in less, while their opponents hallucinate altruism or believe that treaties are ontologically basic objects.
I think you are wrong to say that utilitarians are generally classified as realists. They are only erratically so classified. When you say “even though both make ethical claims reducible to psychological claims,” it sounds like you are defining realism as cognitivism.
As for common language, I think what HM means is that a “realist” is usually someone who denies the existence of things, such as fairies. When people in international relations hold a realist) stance, they aren’t saying that they believe in something that their opponents don’t (as philosophers would), but that they believe in less, while their opponents hallucinate altruism or believe that treaties are ontologically basic objects.
I think you are wrong to say that utilitarians are generally classified as realists. They are only erratically so classified. When you say “even though both make ethical claims reducible to psychological claims,” it sounds like you are defining realism as cognitivism.