Drugs, evolution and the brain

[N Tasker <pia03nt@sheffield.ac.uk>]

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Same article ('Henri Bergson and Aldous Huxley') but dressed up with a new and
flashy title to get your attention! Come on philosophy of mind experts!

Henri Bergson argued for a dualistic theory of mind which says that what exists
is 'life' and 'matter'. He accompanies this with an interesting theory of
perception. When we perceive an object, "we are actually placed outside
ourselves; we touch the reality of the object in an immediate intuition." In
fact, "pure perception is really part of matter, as we understand matter." The
role played by the brain is simply to limit our conscious perception to what is
of most interest, where this is taken to mean those objects which have
practical relevance or aid our survival.

Could what is of value in this theory be preserved in a materialistic theory of
mind? We could say that certain parts of the brain serve to sieve through the
vast quantity of sensory data, selecting for our conscious attention only those
data which are of practical interest. To my mind, such a claim is intuitively
appealing: your skin is in contact with your clothes all day, but how often are
you actually aware of the texture of your shirt? 

Perhaps there is even a reason to extend the thesis to include all phenomenal
experiences rather than just sensory data. Injured people often claim that they
feel little pain; perhaps evolution has equipped us with a 'pain override'
function when a warning that damage has occurred would be useless. Similarly,
many climbers report that sometimes they feel no fear despite being in very
dangerous situations; if the function of fear is to encourage us to seek
safety, and if one happens to be in a situation where the only way achieve
safety is risky and requires fearless confidence, or if one is powerless to do
anything, e.g. caught in an avalanche, then perhaps fear experiences can get
filtered out.

Aldous Huxley was an admirer of Bergson's theory, seeing in it an account of
the
effects of hallucinogenic drugs, meditative states etc. "Disease, mescaline,
emotional shock, aesthetic experience and mystical enlightenment have the
power, each in its different way...to inhibit the functions of the normal self
and its ordinary brain activity, thus permitting the 'other world' to rise to
consciousness." (Letter written to Humphry Osmond in 1953. Printed in 'Moksha',
ed. Michael Horowitz)

Users of hallucinogenic drugs often report becoming fascinated with what we
ordinarily take to be insignificant objects, sometimes seeing intense textural
details in clothing, skin etc. My argument is that if a human being is capable
of perceiving such minute detail when in certain mental states, then the visual
anatomy must be capable of perceiving such detail at any point. The fact that
we don't ordinarily notice these features of the world around us shows that
there must be some mechanism which filters them out of conscious experience. Of
course, such a theory is easily reconciled with evolution. Creatures with
brains which direct their consciousness to those phenomena which are relevant
to survival, will survive to reproduce. Conversely, cave men who spend hours
admiring the shape of their thumbs get eaten by sabre-tooth tigers.

I believe that the crucial thesis can easily be reconciled with a materialistic
view of the mind, sits comfortably alongside the theory of evolution by natural
selection, and has a peculiar ability to account for the effects of drugs and
claims of visionary experiences. How would the claim that a part of the brain
serves as a limiter of conscious experince to that which is most relevant to
survival fit in with the latest theories of mind? 

Nick 


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