In many areas of dispute between realism and antirealism, realism is the natural metaphysical position. We begin as realists about the external world or the unobservable entities mentioned in well-confirmed scientific theories. Generally, people become antirealists about these things (if they do) because they become convinced that realism is in some way naive and must be abandoned in the face of compelling metaphysical and epistemological objections. So too, I think, in ethics. We begin as (tacit) cognitivists and realists about ethics. Moral claims make assertions, which can be true or false; some people are morally more perceptive than others; and people’s moral views have not only changed over time but have improved in many cases (e.g., as regard slavery). We are led to some form of antirealism (if we are) only because we come to regard the moral realist’s commitments as untenable, say, because of the apparently occult nature of moral facts or because of the apparent lack of a well developed methodology in ethics.
David Brink, Moral Realism and the Foundations of Ethics, Cambridge, 1989, p. 23