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.
Plato's unwritten doctrines
According to the prevailing view of researchers today, although the two principles are considered elements of a finally monistic system, they also have a dualistic aspect. This is not contested by defenders of the monistic interpretation but they assert the dualistic aspect is subordinated to a totality that is monistic. Its dualistic nature remains because not only the One but also the Indefinite Dyad is treated as a fundamental principle. Giovanni Reale emphasized the role of the Dyad as a fundamental origin. He thought, however, that the concept of dualism was inappropriate and spoke of a 'bipolar structure of reality.' For him, however, these two 'poles' were not equally significant: the One 'remains hierarchically superior to the Dyad.' Heinz Happ, Marie-Dominique Richard, and Paul Wilpert argued against every derivation of the Dyad from a superior principle of unity, and consequently contended that Plato's system was dualistic. They believe that Plato's originally dualistic system was later reinterpreted as a kind of monism.