The mind-body dualism, in its original and most radical formulation, is the philosophical view that mind and body are fundamentally distinct kinds of substances or natures. That version, now often called substance dualism, implies that mind and body not only differ in meaning but refer to different kinds of entities. Thus, a mind-body dualist would oppose any theory that identifies the mind with the brain, conceived as a physical mechanism.
French philosopher and mathematician René Descartes gave dualism its classical formulation. Beginning from his famous dictum cogito, ergo sum, Descartes developed a theory of mind as an immaterial, non-extended substance that engages in various activities or undergoes various states such as rational thought, imagining, feeling (sensation), and willing. While a number of philosophers before him believed in a ‘psyche’ separate from the body, Descartes was the first to approach it in a systematic way. In simpler terms, his theory derived that humans are capable of reasoning because they have minds as well as physical bodies while anything without a mind is only a material with the physical body.
