One of philosophy's central puzzles is the question of how mental aspects of reality relate to the physical aspects of reality. On the one hand there are things such as thoughts, beliefs, experiences, consciousness, representation and meaning. On the other hand there are sensory stimulations, bodily movements and the location and nature of objects such as molecules and cells and mountains and stars. Very roughly, there are three philosophical approaches to this question. One is to take the mental as fundamental, and account for the rest of the world as a projection of our experience, or a creation of mind or spirit, or something that only has a nature relative to our concepts, or practices of investigation, or something else that seems equally mental. This approach has traditionally been known as “idealism”, although some contemporary idealists prefer to identify themselves as “anti-realists”. The second approach is to take the mental and physical aspects of reality to be equally fundamental, with neither to be accounted for solely in terms of the other. In this approach, one of the important jobs of philosophy is to chart the relationships between the two. This sort of approach is often labelled “dualism” about the mind, since traditional versions of this view held that mind and matter were the two fundamental aspects of the world. A final approach, often known as “materialism” or “physicalism” about the mind, takes only the material or physical to be fundamental, and takes it that all the mental aspects of the world are to be accounted for in material or physical terms.