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IN THE present chapter, we turn from the radically materialistic and radically
idealistic conceptions of the body-mind relation, which we have now seen to be
untenable, and pass to an examination of two versions of the conception of it
termed Psycho-physical Parallelism.
1. Mind and body as in "pre-established harmony"
The "pre-established harmony"
conception of the connection between the series of mental events and the series
of bodily events goes back to Leibnitz. According to him, only "monads"
exist-simple, unextended "substances" whose essence consists in the power of
action and whose exercise of this power consists in having ideas. A substance,
however, is conceived by him as well as by others in his day as something wholly
self-dependent and therefore as incapable of influencing or of being influenced
by the activities of other substances. Hence the monads "have no windows"
through which anything might come in or go out. The sequence of their ideas
proceeds solely out of their own internal, i.e., psychological activity. The
material world consists of masses of monads, whose aggregations, separations,
and motions are determined, not like the internal states of each monad by mental
causes, but solely by mechanical ones. Yet, harmony obtains between the
succession of ideas in a given monad, and the motions of it and of the other
monads associated with it in what we call its body. On this view, the
correlations which obtain between a man's mental states and his bodily states -
for example, that a pin prick and pain, or that volition to move the arm and
motion of the arm regularly go together notwithstanding that neither causes the
other - is analogous to the correlation which obtains between the motions of the
hands of two clocks notwithstanding that neither clock causes the other to
behave as it does.
The explanation of the harmony between the behavior of the two is of course that
it was preestablished by the maker of the clocks, who so constructed and so set
them that they would keep time to each other. Similarly, on the Leibnitzian
view, the harmony which obtains between the series of a man's bodily states and
the series of his mental states is due to its having been preestablished by
man's maker, God.
It is perhaps unnecessary to comment on this quaint conception beyond saying
that no evidence at all exists that body and mind are each inherently incapable
of influencing the other; nor is there any evidence that the harmony which
obtains between them was preestablished by a cosmic clock maker.
But even if this should somehow happen to be the case, nothing at all could be
inferred from it as to whether or not mental life continues after the body dies.
For inferences as to this could be drawn only if one knew-whereas in fact one
does not first that such a divine "clockmaker" as postulated by the
preestablished harmony conception exists; and only if one knew in addition what
his will is as to survival, or not, of man's or of some men's minds after death.
On the other hand, if one supposes the connection - or more properly then simply
the correlation - between the bodily and the mental series of events to be a
purely de facto parallelism; that is, one neither due to causation of the events
of either series by those of the other, nor due to causation of both series by
some one same cause distinct from both as in the preestablished harmony
conception; then, ex hypothesi, termination of either series would have no
effect at all on the other. Termination of the bodily series might, or might
not, de facto, be paralleled by termination also of the mental series. From
purely de facto parallelism in the past and present, nothing at all can be
inferred as to the future.
2. Mind and body as two aspects of one same thing
Still another conception of
the connection between mind and body is of the type envisaged by Spinoza, but
divorced in the writings of contemporary biologists and psychologists that
accept it from the theological hypothesis in terms of which Spinoza phrased it.
The connection in view is of the so-called "double aspect" kind, analogous to
that which obtains, for example, between the two sides of a sheet of paper.
There, a creasing of the sheet appears as a ridge on one side, and automatically
and simultaneously as a valley on the other side, although the ridge does not
cause the valley nor the valley the ridge.
If the paper analogy is used at all, however, its additional features also must
be considered; for example, the fact that a spot of color on one side is not
necessarily matched by a difference of any kind on the other side. The
implication of the paper analogy as regards the "double aspect" conception of
the connection between body and mind is then that one cannot tell whether the
difference on the material side, which cessation of the body's life constitutes,
is or is not automatically matched on the other side by cessation of
consciousness, unless one knows independently what the entity or substance is,
of which body and mind are alleged to be two "aspects;" and knows what
properties it, as distinguished from either of its aspects, has. For only such
knowledge would enable one to judge whether the body's death is analogous to,
say, the ridging of one side of the paper - which, because of the properties of
the paper sheet, is automatically matched by a valleying of the other side - or
is analogous on the contrary to the staining of one side - which, again because
of the properties of the paper sheet, is not automatically matched by any change
on the other side.
In short, the supposition that body and mind are two "aspects" of one same thing
is wholly metaphorical; and unless and until the metaphor has been translated
into literal terms identifying for us the entity or substance itself, of which
brain and mind are supposed to be two "aspects," nothing can be inferred as to
whether the material change - death of the brain - is or is not automatically
matched by death of the mind.
But no substance or thing having body and mind as two aspects has ever yet been
exhibited, both aspects of which could be so experimented upon that one might
discover what kinds of changes, if any, and of which aspect, are or are not
automatically paralleled by changes of the other aspect.
Moreover, if it were suggested, as occasionally it is, that the body itself or
the brain is that substance, and that mental activity is brain activity, but
"viewed from within" - from the inside instead of the outside - then the
appropriate comment would obviously be that the word "inside" as so used really
means nothing at all. For, if one wishes to observe what goes on literally
inside the brain, what one must do is simply to open it up and look. Such an
operation might, in a then facetiously etymological sense of the word, be termed
"Introspection," but would anyway be something radically different from what in
fact is denominated Introspection.
Thus, although the "double-aspect" description of the connection between mind
and brain or mind and body has found favor with a number of biologists and
psychologists, it turns out on examination to be nothing but a vacuous metaphor,
from which nothing at all follows as to whether or not mental life can continue
after death.
3. Mental activity as a function
of cerebral activity
A statement currently
much in vogue is that mental activity is a function of the activity of the brain
and nervous system.
The word "function," (from L. fungere, to perform) has a variety of meanings,
some of which are not wholly distinct from certain of the others. Most broadly,
when two things, A and B, each of which admits of variations, vary
concomitantly, i.e., in such manner that variation of kind or/and magnitude V
(a) of A, and variation of kind or/and magnitude V (b) of B, occur regularly
together, then the two sets of variations are said to be functionally related;
and either can be said to be a function of the other.
If, however, the variations given, or instituted, are, say, those of A, and the
variations then observed those of B, then B is termed the dependent variable and
A the independent variable.
If the variations of one of the two functionally related variables, say, those
of B, occur after the variations of A of which they are functions, then
ordinarily the dependence of the variations of B upon those of A is causal
dependence, direct or indirect. This, apparently, is the meaning which
"dependent upon" is intended to have in Webster's definition of one of the
senses of "function of" as: "any quality, trait or fact so related to another
that it is dependent upon and varies with that other." This sense is usually the
one in which thought, or mental activity, is said to be a function of brain
activity; and in which it is said that the specific function of the brain is to
"perform" the various mental activities - thinking, perceiving, remembering,
etc.
In the light of these remarks, it is evident that to speak of mental activity as
a function of brain activity is not to offer a new description of the connection
between the two, different from all those already mentioned; for each of these
asserts that brain states and mental states are functionally related: If the
functional dependence is causal, and of mental activity on brain activity, then
this is the type of connection, i.e., of function. which epiphenomenalism
describes. If the dependence is causal, but is of brain activity on mental
activity, then this type of functional relation would be describable as hypophenomenalism - the exact converse of epiphenomenalism. If the functional
dependence is causal, but not exclusively either of mental upon cerebral states,
or of cerebral upon mental states, then what we have is psycho-physical
interactionism. Lastly, if the functional dependence is not causal, then it
constitutes parallelism of one or another of the types described in what
precedes, from which, as we have seen, nothing can be inferred as to whether
survival of the mind after death is or is not possible.
We shall now consider in turn epiphenomenalism, hypophenomenalism, and
interactionism.
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