 In sum: Suppose we understand moral naturalism to be the view that moral facts are natural. And suppose we say, in a rough and ready way, that a fact is natural just in case it pulls its explanatory weight in the natural sciences (see Wiggins 1993). Reid maintains that Newtonian methods exhaust the limits of natural science. Newtonian science, however, does not investigate the ends or rational principles for which we act. The ends for which we act neither fall under Newtonian laws nor are identical with them. But moral facts, Reid says, are among the ends or rational principles for which we act. It follows that, in Reid’s view, moral facts are not the proper object of scientific inquiry. The moral domain is autonomous.