  Moore is the intuitionist who laid most stress on the non-natural nature of moral properties, though his focus was on goodness rather than rightness. In Principia Ethica Moore defines a natural property as one that can exist by itself in time and not merely as a property of some natural object (1903/1993a, 93). The idea is, then, that natural properties, such as the pleasantness or squareness of an object, can exist independently of that object, whereas the goodness of a good thing cannot exist independently of that thing.