It
seems to us sometimes as though the phenomena of personal
experience were in a way phenomena in the upper strata of the
atmosphere as opposed to the material phenomena which happen on the
ground. There are views according to which these
phenomena in the upper strata arise when the material phenomena
reach a certain degree of complexity.
E.g
., that the mental phenomena,
sense experience, volition, etc., emerge when a
type of animal body of a certain complexity has been
evolved. There seems to be some obvious truth in this,
for the amoeba certainly doesn't speak or write or
discuss, whereas we do. On the other hand the problem
here arises which could be expressed by the question:
“Is it possible for a machine to
think?” (whether the action of this machine can be
described and predicted by the laws of physics or, possibly,
only by laws of a different kind applying to the behaviour of
organisms). And the trouble which is expressed in
this question is not really that we don't yet know a
machine which could do the job. The question is not
analogous to that which someone might have asked a hundred years
ago: “Can a machine liquefy a
gas?” The trouble is rather that the
sentence, “A machine thinks” (perceives,
wishes) seems somehow nonsensical. It is as
though we had asked “Has the number 3 a
colour?” (“What colour could it be,
as it obviously
79.
has none of the colours
known to us?”) For in one aspect of the
matter, personal experience, far from being the
product
of physical, chemical, physiological processes, seems to be the
very
basis of all that we say with any sense about such
processes. Looking at it in this way we are inclined to
use our idea of a building-material in
yet
another misleading way, and to say that the whole world, mental and
physical, is made of one material only.