<P> The central claim of what is often called Cartesian dualism, in honor of Descartes, is that the immaterial mind and the material body, while being ontologically distinct substances, causally interact . This is an idea that continues to feature prominently in many non-European philosophies . Mental events cause physical events, and vice versa . But this leads to a substantial problem for Cartesian dualism: How can an immaterial mind cause anything in a material body, and vice versa? This has often been called the "problem of interactionism ." </P> <P> Descartes himself struggled to come up with a feasible answer to this problem . In his letter to Elisabeth of Bohemia, Princess Palatine, he suggested that spirits interacted with the body through the pineal gland, a small gland in the centre of the brain, between the two hemispheres . The term "Cartesian dualism" is also often associated with this more specific notion of causal interaction through the pineal gland . However, this explanation was not satisfactory: how can an immaterial mind interact with the physical pineal gland? Because Descartes' was such a difficult theory to defend, some of his disciples, such as Arnold Geulincx and Nicholas Malebranche, proposed a different explanation: That all mind--body interactions required the direct intervention of God . According to these philosophers, the appropriate states of mind and body were only the occasions for such intervention, not real causes . These occasionalists maintained the strong thesis that all causation was directly dependent on God, instead of holding that all causation was natural except for that between mind and body . </P> <P> During the 19th and 20th centuries, materialistic monism became the norm . Still, in addition to already discussed theories of dualism (particularly the Christian and Cartesian models) there are new theories in the defense of dualism . Naturalistic dualism comes from Australian philosopher, David Chalmers (born 1966) who argues there is an explanatory gap between objective and subjective experience that cannot be bridged by reductionism because consciousness is, at least, logically autonomous of the physical properties upon which it supervenes . According to Chalmers, a naturalistic account of property dualism requires a new fundamental category of properties described by new laws of supervenience; the challenge being analogous to that of understanding electricity based on the mechanistic and Newtonian models of materialism prior to Maxwell's equations . </P> <P> A similar defense comes from Australian philosopher Frank Jackson (born 1943) who revived the theory of epiphenomenalism which argues that mental states do not play a role in physical states . Jackson argues that there are two kinds of dualism . The first is substance dualism that assumes there is second, non-corporeal form of reality . In this form, body and soul are two different substances . The second form is property dualism that says that body and soul are different properties of the same body . He claims that functions of the mind / soul are internal, very private experiences that are not accessible to observation by others, and therefore not accessible by science (at least not yet). We can know everything, for example, about a bat's facility for echolocation, but we will never know how the bat experiences that phenomenon . </P>

Who believed that the mind and body were linked