Philosophy of mind
Dualism is a set of views about the relationship between mind and matter (or body). It begins with the claim that mental phenomena are, in some respects, non-physical. One of the earliest known formulations of mind–body dualism was expressed in the eastern Sankhya and Yoga schools of Hindu philosophy (c. 650 BCE), which divided the world into purusha (mind/spirit) and prakriti (material substance). Specifically, the Yoga Sutra of Patanjali presents an analytical approach to the nature of the mind.
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.