Final answer:
Rene Descartes' concept of dualism is explained as the division of existence into two distinct realms: the non-physical mind and the physical body, which are fundamentally different substances.
Step-by-step explanation:
Rene Descartes' concept of dualism is best described by the separation of the mind and body into distinct entities. Descartes, a substance dualist, posited that there are two fundamental and irreducible realities: the physical (res extensa) and the non-physical or spiritual (res cogitans).
He famously concluded 'Cogito, ergo sum: I think, therefore I am,' suggesting the existence of the mind as a thinking thing independent of the physical body. Descartes' dualism maintains that the mind, or the 'thinking thing,' is non-physical and can exist apart from the physical brain, whereas the body is a non-thinking, extended substance.