  Along with its moral epistemology, a distinctive feature of intuitionist thought is its non-naturalist realism. Intuitionists maintain that moral judgements are cognitive states, and that some at least of these judgements are true. They are true when the things referred to have the moral property that is ascribed to them by the judgement. The moral properties that intuitionists tended to focus on were the thin moral properties of goodness and rightness. These properties are, they maintained, simple, non-natural properties. It is not always clear how they understood the notion of a non-natural property (more on this below), but for now we can say that they denied that moral properties can be defined wholly in terms of psychological, sociological, or biological properties. Some intuitionists allowed that goodness can be defined in terms of rightness (Sidgwick and Ewing) or rightness in terms of goodness (early Moore). But all intuitionists maintained that at least one of these moral properties is simple, or indefinable.