David Rosenthal

Dualism is the view that mental phenomena are, in some respect, nonphysical. The best-known version is due to Descartes, and holds that the mind is a nonphysical substance. Descartes argued that, because minds have no spatial properties and physical reality is essentially extended in space, minds are wholly nonphysical. Every human being is accordingly a composite of two objects: a physical body, and a nonphysical object that is that human being's mind. On a weaker version of dualism, which contemporary thinkers find more acceptable, human beings are physical substances but have mental properties, and those properties aren't physical. This view is known as property dualism, or the dual-aspect theory