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Time to move beyond the mind-body split

BMJ 2002; 325 doi: (Published 21 December 2002) Cite this as: BMJ 2002;325:1433

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Descartes and mind-body dualism


In essence, by saying that mind and matter are very different, and
dividing “the aspects of single experience into separate entities – the
fatal doctrine of Descartes…spoke of mind and body, thought and its
object, matter and mind, as though they were independent existents.”
[Berlin, 381] Unfortunately, since that time, science has proceeded in the
blind belief that he thought mind is entirely reducible to matter; he did
not. They are blatantly different things.

For example, physical substance [res extensa] is composed of matter,
propelled by energy, extensive in space and locatable in time and though
we might say mind [res cogitans] also consists of mental matter, propelled
by mental energy and occupying mental space, yet mental time is a wholly
different thing than time as we know it in the physical universe. There is
a fundamental incompatibility between the two categories: one which is
conscious and perceives and one which is unconscious and unperceiving,
which “lacks subjective awareness, purpose or spirit.” [Tarnas, 278]

Descartes sought to reveal that “an immaterial reality exists
alongside the material…[and] some way of connecting the two worlds,”
[Rogers, 236] must be found. Mental matter does not resemble physical
matter, as it does not seem to occupy space or have any measurable mass or
location. Even on this basis the differences between the two are clear:
“Descartes’ dualism, the sharp differences he draws between mind and body
with their irreconcilable attributes of thought and extension, [Rogers,
236] define them as different things, which behave differently. The notion
of “matter on the one hand and of mind or spirit on the other were brought
into sharp relief,” [Rogers, 236] through his meditations on this problem.

By this separation, which Descartes initiated, “science was left to
follow its bent in the physical universe.” [Rogers, 236] Locke, Newton and
their successors tended only to see the material aspects of Descartes’
views and that is a pity because the stark freshness and originality of
Cartesian dualism is still obvious when stated simply. Though both are
real, they each operate under very different ‘rules:’
“mind and matter so totally different in their nature.” [Rogers, 250] One
might therefore easily argue that, “Descartes and Locke are evidently
mistaken, mind is not a wax tablet…it is not an object, but a perpetual
activity which shapes its world.” [Berlin, 569]

However, what is obvious is that some relationship between brain and
mind must exist, forming a two-way street with traffic moving freely in
both directions. To believe wholeheartedly that solely the brain, and
chemical changes in it, causes all mental events, and that mind disappears
like smoke at the point of death, then I am sorry but these never were the
views of René Descartes. Maintaining that there must be “a mutual
influence between the soul and the body,” [Rogers, 253] and that it is in
“the human organism that matter and mind come into closest contact,”
[Rogers, 250] thus it is this “relationship of mind and body that
justifies a distinction between two classes of conscious fact.” [Rogers,

Cartesian dualism still allows for mind as a spirit-like immaterial
being that can survive death and have some kind of afterlife; such is
certainly permitted by Descartes and many philosophers even after 1700. If
mind were solely a product of molecules, then clearly its genetic
component would be much more prominent than it is. Within families, for
example, it is not possible to show the type of strict determinism of
personality the theory would require. Instead of mental conformity of
close relations, we find diversity. Therefore, the genetic basis of mind
remains doubtful and unproven. Likewise, identical twins would show very
little mental differences. Again, this is not observed and indeed, many
such twins show remarkable differences in personality in spite of being
identical at the molecular level.

Due to the above considerations, mind-body dualism and molecular
basis of mind are fraught with problems. The current scientific fancy that
mind is solely a product of matter, that mental activity must be reducible
solely, and exclusively to brain events and brain chemistry, never did
flow from Descartes, but from the materialistic science of his successors.
The argument for a strict molecular basis of mind remains an act of pure
belief no different from the religious belief that mind is an immortal
soul that transmigrates from body to body and lifetime to lifetime, or
belief in angels or fairies.

In spite of all claims pinned to him by his successors, Descartes
remained a basically religious man. By asserting “the undeniableness of
consciousness,” [Rogers, 246] and expressing a belief in “God as a
substance infinite, eternal, immutable, independent, omniscient,
omnipotent,” [Rogers, 247] Descartes had actually “left the world divided
into three constituent parts – the two substances, mind and matter, and a
third more ultimate reality, God,” [Rogers, 253] being quite insistent
that “mind and matter…are not to be conceived apart from God,” [Rogers,
253] who Descartes regarded, perhaps old-fashioned, as “a perfect infinite
being.” [Tarnas, 277]


Sir Isaiah Berlin, The Proper Study of Mankind an Anthology of
Essays, London: Pimlico, 1998

Arthur K Rogers, A Student’s History of Philosophy, New York:
Macmillan, 1960

Richard Tarnas, The Passion of the Western Mind, London: Pimlico,

Competing interests:  
None declared

Competing interests: No competing interests

05 January 2003
Peter Morrell
freelance researcher, history of medicine, UK