Philosophers have been battling with the mind for centuries. In the Seventeenth Century, René Descartes posited a duality between the mind and the body. According to Descartes, matter is material and the mind is immaterial. The Princess of Bohemia, Elisabeth, then asked an explanation as to how it is the mind could then causally act upon the body and vice versa. Descartes’s response was that they are connected through the pineal gland. But this led to a regressive causal chain that never fully satisfied the connection between substance and the soul. Metaphorically, we see this sort of fragmentation in the theories of 20th Century psychoanalysts. Sigmund Freud proposed a splitting of the mind into three parts: the id, the ego, and the superego.
A more literal contemporary manifestation of Cartesian thought is dualism of the present-day. David Chalmers, a philosopher of the mind, believes that everything is material and natural, but mind-stuff and matter-stuff are nevertheless distinct. What it is to be constitutive of the mind is altogether different from what it is to be an arm or a leg. From this stems epiphenomenalism, the theory that mind-stuff, and only mind-stuff, produces mental states and mental actions. These states are not, however, reducible to the material stuff whence they came.
Naturalistic dualism sits in contrast to other theories of mind like identity theory and functionalism. These are the theses that (i) a mind is constitutive of types we can assign to mind-stuff (like thinking, processing, remembering), and (ii) mental states are whatever takes the form of mental states (we might assign a mental state to that of ‘being in pain’), respectively. Functionalists, in particular, would agree that machines can think. That is, if a computer could replicate or produce all the mental states required of a mind, in spite of its being made of silicon and circuit boards, it can be said to have a mind.
For all the theories there are about what makes a mind a mind, or what it is to have one, it still feels as if something is amiss. As Thomas Nagel suggests, the mystery of the mind can be captured in just a line — “what is it like?” Well, we may never know. But in the process, we can keep reading about it.
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