  Some of these characterizations can be put to one side rather easily. For example, the thesis that natural properties must be capable of existing by themselves in time [(v) above] seems to make the very idea of a natural property deeply problematic. As C.D. Broad argued (see Broad 1942), it is unclear how the roundness and brownness of a penny, for example, could exist in time by themselves. In light of this objection, Moore himself eventually abandoned this way of characterizing natural properties (Moore 1942: 581–582). Understanding natural properties as those studied by the natural sciences [(i) above] threatens to make our characterization of the natural implausibly dependent on what the actual objects of scientific investigation happen to be, as if there could not be natural properties our actual scientific investigation somehow never discovered. It also makes it unclear why moral philosophy is not one of the sciences (Baldwin 1985: 26). We could try to finesse this point by holding that natural properties need not actually be the subject matter of the natural sciences but instead only must be fit for investigation by the natural sciences but this characterization is simply not very illuminating. For it cries out for a characterization of what makes something fit for study by the natural sciences, and that further characterization seems likely to do all the work in explaining what is involved in a property being natural.