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.
Mortimer J. Adler
Adler was a self-proclaimed "moderate dualist", and viewed the positions of psychophysical dualism and materialistic monism to be opposite sides of two extremes. Regarding dualism, he dismissed the extreme form of dualism that stemmed from such philosophers as Plato (body and soul) and Descartes (mind and matter), as well as the theory of extreme monism and the mind–brain identity theory. After eliminating the extremes, Adler subscribed to a more moderate form of dualism. He believed that the brain is only a necessary, but not a sufficient, condition for conceptual thought; that an "immaterial intellect" is also requisite as a condition; and that the difference between human and animal behavior is a radical difference in kind. Adler defended this position against many challenges to dualistic theories.