Mind–body dualism
Ontological dualism makes dual commitments about the nature of existence as it relates to mind and matter, and can be divided into three different types:Substance dualism is a type of dualism most famously defended by René Descartes, which states that there are two kinds of foundation: mental and body. This philosophy states that the mental can exist outside of the body, and the body cannot think. Substance dualism is important historically for having given rise to much thought regarding the famous mind–body problem. Substance dualism is a philosophical position compatible with most theologies which claim that immortal souls occupy an independent realm of existence distinct from that of the physical world.
Trialism
Cottingham introduced trialism after citing that Descartes' account of sensation and imagination has opened his official dualism under considerable pressure. He cited that an evaluation of the Cartesian writings on human psychology there is a grouping of not two but three notions - mind, body, sensation, hence the term trialism. According to cottingham, Descartes added the third category or notion " alongside thought and extension without proceeding to reify it as a separate substance." Thinkers such as Daniel Garber and Tad Schmaltz supported this by citing a letter in the correspondence between Descartes and Princess Elizabeth of Bohemia, which indicated that that he changed his mind from a dualistic view.