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THE CONTENTION considered in the preceding chapter was that the processes
constituting the living body's minimal, i.e., vegetative, life are autotelic
objective expressions of blind cravings of mind or minds to organize matter.
Such of these blind cravings as are present in the human mind might be termed
its vegetative conations, as distinguished from its distinctively animal and
human ones.
The hypophenomenalistic contention was of interest to us primarily because of
the superiority, in the respects we noticed, of the alternative it provides to
the contention that the life of living things is a purely physico-chemical
process and that a mind and its various conations and states are mere
epiphenomena of those processes in the living brain. We shall not, however, need
to occupy ourselves further with hypophenomenalism since the question to which
it is an answer is different from the question central for us in these pages.
The latter question has to do with the nature of the relation between two terms.
One of them is a living human body - no matter whether its being "alive" be a physico-chemical epiphenomenon or be a hypophenomenon of some primitive
conations. The other term of the relation is constituted by existence and
exercise of the animal and especially of the typically human capacities or
"dispositions" in a person's total mind conceived in the manner set forth in
Chapter VI. Man's living material body is of course a necessary, even if not a
sufficient, factor in the development of his mind from the rudimentary state in
which it is at the birth of his body. But our problem is whether on the one hand
a person's living body, and on the other the part of that person's mind
consisting of the distinctively human capacities peculiar to him, are so related
that, once those capacities have been acquired by him, they, or some of them.
can continue to exist and to function after that body dies.
Interactionism, as conceived in these pages, answers that no
impossibility - either theoretical or empirical - is involved in so supposing. Let
us, however, first consider the classical account of mind-body interaction.
1. Interaction as conceived by Descartes
The contention that the human mind and
the living human body can, and to some extent do, act each on the other is
associated chiefly with the name of Descartes. His account of their interaction,
however, is burdened with difficulties that are not inherent in interactionism
but arise only out of some of the peculiarities of his formulation of it.
The most troublesome of these is that mind and body are conceived by Descartes
as each a "substance" in the sense that, aside from the dependence of each on
God, each is wholly self-sufficient. This entails that changes in the state of
either cannot without inconsistency be supposed to cause changes in the state of
the other. Descartes, in one of his letters, acknowledges this(1). Nevertheless
he asserts that such causation does occur: "That the spirit, which is
incorporeal, is able to move the body, no reasoning or comparison from other
things can teach this to us. Nevertheless, we cannot doubt it, for experiments
too certain and too evident make us clearly aware of it every day; and one must
well notice that this is one of the things that are known of themselves [Une des
choses qui sont connues par elles memes] and that we obscure them every time we
would explain them by others."(2)
(1) Letter of June 28, 1643, to Elizabeth. Descartes' Correspondence, ed. Adam Milhaud, Vol. 5:324.
(2) Letter VI, Vol. 2:31.
Yet, as if to mitigate the illegitimacy which, on Descartes' conception of
substance, attaches to interaction, he insists that it occurs only at one place.
This is at the center of the brain, in the pineal gland, which he holds is the
principal "seat" of the soul. The deflections of it by the "animal spirits,"
Descartes says. cause perceptions in the soul; and, conversely, the soul's
volitions deflect the pineal gland and thereby the "animal spirits," whose
course to the muscles causes the body's voluntary movements.
But to pack into the meaning of the word "substance" the provision that one
substance cannot interact with another is - here as in the historical
precedents-quite arbitrary; for no theoretical need exists to postulate any
substance as so defined; nor is the term, as so defined, applicable to anything
actually known to exist. As ordinarily used, the term denotes such things as
water and salt, steel and wood, nitric acid and copper, which can and on
occasion do interact. Indeed, all the dispositions (except internal ones) in
terms of which the nature of any substance analyzes consist of capacities of the
substance concerned to affect or to be affected by some other substance.
Thus, the paradox Descartes finds in the interaction which he anyway
acknowledges occurs between body and mind, arises only out of his gratuitously
degrading to the status of "modes" the things ordinarily called "substances" -
which do interact - and, equally gratuitously, defining "substances" as incapable
of interacting.
2. Interaction and the heterogeneity of mind and body
What causes Descartes to
find paradoxical the interaction of mind and body and yet to find no difficulty
in the interaction of substances such as steel and wood, etc., is that, in the
latter cases, the two substances concerned. being both of them material, are
ontologically homogeneous; whereas body and mind - being one of them res extensa
and the other res cogitans - are ontologically heterogeneous.
But the supposed paradox of interaction between them evaporates as soon as one
realizes that the causality relation is wholly indifferent to the ontological
homogeneity or heterogeneity of the events figuring in it as cause and as
effect. This indifference or neutrality holds no matter whether causality be
defined, as later by Hume, as consisting in de facto regularity of sequence; or
more defensibly, as in experimental procedure, in terms of a state of affairs
within which only two changes occur - one, called "cause," occurring at a given
moment, and the other, occurring immediately thereafter, called "effect." All
that the causality relation presupposes as to the nature of its cause-term and
its effect-term is that both be events, i.e., occurrences in time. Hence, as
Hume eventually pointed out and as we have insisted, an event, of no matter what
kind, can, without contradiction or incongruity, be conceived to cause an event
of no matter what other kind. Only experience can tell us what in fact can or
cannot cause what. That, as experiment testifies, volition to raise one's arm
normally causes it to rise, and burning the skin normally causes pain, is not in
the least paradoxical.
3. H. S. Jennings on interaction between mind and body
The interactionist views
of the eminent biologist, H. S. Jennings, are free from the artificial
difficulty present in those of Descartes, and are far clearer and more critical
than those of most of the biologists who have expressed themselves on the
subject of the relation between body and mind.
In an address, Some Implications of Emergent Evolution, which he delivered in
1926 as retiring chairman of the Zoological Section of the American Association
for the Advancement of Science, and later in a book, The Universe and Life(3),
Jennings sharply distinguishes two conceptions of determinism. He calls them
respectively "radically experimental determinism" and "mechanistic determinism."
The latter is the one commonly entertained by scientists, and is to the effect
that whatever occurs in the universe, whether novel or not, is theoretically
explicable in terms of the properties and relations of the elementary
constituents of matter; and hence that even radical novelties such as the advent
of life in an until then lifeless world are the inherently predictable necessary
or probable effects of certain collocations - that is, are predictable in principle
even if not in fact by us at a given time for lack of the required empirical
data. This - except for the substitution of probabilities for necessities at the
subatomic level in consequence of the state of affairs recognized in
Heisenberg's principle of indeterminacy - is essentially determinism as
conceived in Laplace's famous statement we have quoted earlier, that "an
intelligence knowing, at a given instant of time, all forces acting in nature,
as well as the momentary positions of all things of which the universe consists,
would be able to comprehend the motions of the largest bodies of the world and
those of the smallest atoms in one single formula, provided it [i.e., that
intelligence] were sufficiently powerful to subject all data to analysis; to it,
nothing would be uncertain, both future and past would be present before its
eyes."(4)
(3) Yale Univ. Press, New Haven, 1933. The address appeared in
Science, Jan. 14,
1927, and was reprinted with corrections the same year by the Sociological
Press, Minneapolis.
(4) Theorie Analytique des Probabilites, Paris, 3d. edition, 1820.
Obviously, however, such a physico-chemical determinism is in fact only a
metaphysical creed; for it vastly outruns what theoretical physics and physical
chemistry are actually able to predict. What has occurred is that something
which in reality was but a program - namely to explain in physico-chemical terms
whatever turns out to be capable of explanation in such terms - has unawares been
transformed into the a priori creed that whatever does occur is ultimately
capable of being explained in such terms. Doubtless, the enthusiasm resulting
from the truly remarkable discoveries which have been made under that program is
what has brought about the unconscious metamorphosing of the latter into a
creed, i.e., into a belief piously held without adequate warrant both by
scientists and by laymen awed by the vast achievements of science.
On the other hand, the determinism Jennings terms "radically experimental
determinism" does not assume, as physicochemical determinism gratuitously does,
that only physical or chemical events can really cause or explain anything.
Rather, it holds, as did David Hume, that only experience can reveal to us what
in fact can or cannot cause what; and holds further as does the present writer,
that, ultimately, the only sort of experience that can reveal what can or cannot
cause what is experience of the outcome of an experiment: "The only test as to
whether one phenomenon affects another is experiment … the test is: remove
severally each preceding condition, and observe whether this alters the later
phenomena. If it does, this is what we mean by saying that one condition affects
another; that one determines another. Such experimental determinism is not
concerned with likenesses or differences in kind, as between mental and
physical, nor with the conceivability or inconceivability of causal relations
between them; it is purely a matter of experiment."(5)
(5) Some Implications of Emergent Evolution, p. 9 of the reprint. Cf. the
present writer's own analysis of Causality in his Causation and the Types of
Necessity Univ. of Washington Press, Seattle, 1924, pp. 55-6, and in his later
Nature, Mind, and Death Open Court Pub. Co. La Salle, 1951, Ch. 8, Sec. 3, where
he insists that Causality is the relationship, which an experiment exhibits,
between a state of affairs, an only change in it at a time T, and an immediately
sequent only other change in it; and that causal laws are generalizations
obtained by attention to the similarities that turn out to exist between two or
more experiments each of which, in its own individual right, revealed a case of
causation.
Jennings goes on to point out that "if we rely solely upon experiment, the
production of mental diversities by preceding diversities in physical conditions
is the commonest experience of mankind; a brick dropped on the foot yields other
mental results than from a feather so dropped." But "experimental determinism
also holds for the production of physical diversities by preceding mental
diversities; for experimental determinism of the physical by the mental. One
result follows when a certain mental state precedes; another when another mental
state precedes ... No ground based on experimental analysis can be alleged for
the assertion that the mental does not affect the physical; this is a purely a
priori notion. According therefore to radical experimentalism, consciousness
does make a difference to what happens ... the mental determines what happens as
does any other determiner ... Among the determining factors for the happenings
in nature are those that we call mental. Thought, purpose, ideals, conscience,
do alter what happens."(6)
(6) Ibid. p. 10. Cf. The Universe and Life, pp. 33-48.
4. What interactionism essentially contends
The interactionism. that seems to
the present writer to constitute the true account of the relation between the
human mind and the living human body contends, as does Jennings, that each of
the two acts at times on the other. Certain brain events, caused by
environmental stimuli upon the external sense organs or by internal bodily
conditions, cause certain mental events-notably, sensations of the various
familiar kinds. On the other hand, mental events of various kinds (and no matter
how themselves caused) cause certain brain events - those, namely, which
themselves in turn cause or inhibit contractions of muscles or secretions of
glands. But that mind and body thus interact does not entail that each cannot,
or does not at times, function by itself, i.e., without acting on the other or
being acted upon by it. Certainly, many of man's bodily activities-at the least
the vegetative activities-can and do at times go on in the absence of conscious
mental activity or without being affected by such as may be going on at the
time. On the other hand, at times during which the mind is engaged in
reflection, meditation, or reminiscence, and is thus in a state of what is
properly called "abstraction" (from sensory stimulations and from voluntary
bodily actions,) the thoughts, desires, images, and feelings that occur are
directly determined by others of themselves together with the acquired
dispositions or habits of the particular mind concerned.
5. Which human body is one's own
In connection with the interactionist thesis,
it is of particular interest to raise a question which at first sight seems
silly, but the answer to which turns out to be decisive in favor of
interactionism. That question is, How do we know which one of the many human
bodies we perceive is our own?
We might answer that it is the only human body whose nose we always see if it is
illuminated when we see anything else; or that we call that human body our own,
the back of whose head we never can see directly, etc. But this answer would not
be ultimately adequate; for if a human body, the back of whose head we do see
directly, were such that when and only when it is pricked with a pin or
otherwise injured, we feel pain; such that when and only when we decide to open
the door, it walks to the door and opens it; such that when and only when
we
feel shame, it blushes; and so on, invariably; then that body would be the one
properly called our own! And the body, the back of whose head we never see
directly - but whose injuries cause us no pain, and over whose movements
our
will has no direct control - would be for us the body of someone else,
notwithstanding the peculiarity that we never manage to see the back of its head
directly.
Thus when, in the question: What is the relation between a mind and its body? we
substitute for "its body" what we have just found to be the meaning of that
expression, then the question turns out to have implicitly contained its own
answer, for it then reads: What is the relation between a mind and the only body
with which its relation is that of direct interaction? That is, that the
mind-body relation is the particular relation which interactionism describes is
analytically true.
Let us, however, now examine a consideration that has been alleged to rule out
the possibility of interaction between mind and body.
6. Interaction and the conservation of energy
It has often been contended that
the principle of the conservation of energy precludes causation of a mental
event by a material one, or of a material event by a mental one; for such
causation would mean that, on such occasions, a certain quantity of energy
respectively vanishes from, or is introduced into, the material world; and this
would constitute a violation of that conservation principle.
Prof. C. D. Broad, however, has pointed out that no violation of the principle
would be involved if, each time energy vanished from the material world at one
point, an equal quantity of it automatically came into it at another point. Also
that, even if all physico-physical causation involves transfer of energy, no
evidence exists that such transfer occurs also in physico-psychical or
psycho-physical causation(7).
(7) The Mind and its Place in Nature, Harcourt, Brace & Co. New York, 1929, pp.
103, ff.
To this it may be added that if by "energy" is meant something experimentally
measurable, and not just a theoretical construct, then the fact is not that
causation is ascertainable only by observing that energy has been transferred,
but on the contrary that "transfer of energy" is ultimately definable only in
terms of causation as experimentally ascertainable. That is, even if it should
happen to be true that energy is transferred whenever causation occurs,
nevertheless transfer of energy is not what we notice and mean when we observe
and assert that a certain event C caused a certain other event E. For,
obviously, correct judgments of causation have been made every day for thousands
of years by millions of persons who not only did not base them on measurements
of energy, but the immense majority of whom did not have the least conception of
what physicists mean by "energy." Everyone of the verbs of causation in the
common language - to kill, to cure, to break, to bend, to irritate, to remind,
to crush, to displace, etc. - acquired its meaning out of common perceptual
experiences, not out of laboratory measurements of energy. The Toms, Dicks, and Harrys who have witnessed the impact of a brick on a bottle and the immediately
sequent collapse of the bottle judged that the striking brick broke the bottle,
i.e., caused its collapse. And they so judged because the impact of the brick
was prima facie the only change that occurred in the immediate environment of
the bottle immediately before the latter's collapse.
Anyway, as Prof. M. T. Keeton has pointed out, the proposition that energy is
conserved in the material world is not known, either a priori or empirically, to
be true without exception. The "principle" of conservation of energy, or of
mass-energy, is in fact only a postulate - a condition which the material world
must satisfy if it is to be a wholly closed, isolated system. And, when
interaction between mind and body is asserted to be impossible on the ground
that it would violate the "principle" of the conservation of energy, the very
point at issue is of course whether the material world is in fact a wholly
closed, isolated system.(8)
(8) Some Ambiguities in the Theory of the Conservation of Energy,
Philosophy of
Science, Vol. 8, No. 3, July 1941.
Thus, the ground just considered, on which the interactionist conception has
been attacked, quite fails to invalidate it. Nor does the fact that, up to the
time of the brain's death the shaping of the mind has been due in part to
interaction between mind and brain, entail that the conscious and subconscious
mind - such as it has become by the time the body dies - cannot after this
continue to exist and to carry on some at least of its processes.
Interactionism leaves the possibility of this open, but does not in itself
supply evidence that such survival is a fact. Lamont however, argues at length
in the book cited earlier against any dualistic conception of the nature of body
and mind. Examination in some detail of the considerations alleged by him to
rule out dualism must therefore be the subject of our next chapter.
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