MIND, life, body. Each of these three words is in
daily use and each may occur with half a dozen
different meanings in as many sentences. Some of the
meanings belong, moreover, to different universes of
discourse so that mention of mind, life and body may
evoke associations connected with psychology, philosophy,
religion, or, perhaps, with just trivial mundane affairs.
Small wonder then that statements in which the words
are brought together often lead to profound misunderstanding and heated argument.
Much in science is discussed in these terms. For whenever a scientist observes a change of any kind in a material
system lie looks for the cause of the change. Usually this
is complex; so he analyses it into its sundry component
causes and is not satisfied until he has traced every one of
them. Then, and only then, can he give a complete and
rational explanation of the change.
Similar complete and satisfactory explanations can be
found for the paths of the planets, for the tides, for the
formation of valleys and mountains, for the sun's radiation,
for chemical reactions, for the colours of the rainbow.
Thus are scientists slowly and surely completing their
analysis of the causes of all observable changes and giving
thereby a more and more complete statement about the
nature of reality.
The importance of looking for the forces that contribute
to every material change is so great, and science benefited
so enormously when causality came to be discussed in
terms of physical forces, that there is now a risk of overstatement. From the proved fact that some of the component causes of every physical change must be physical
forces it is a small step to the unproved assumption that
all the component causes must be physical forces; but
it is a dangerous step. True, there are very strong reasons
for this assumption, as I shall show in Chapter VII, but
they are not quite conclusive. The assumption remains a
hypothesis and is severely shaken by certain observations
on the behaviour of living substance. These are not
difficult or recondite observations. They are facts of
common knowledge and if their bearing on the nature of
causality has not yet been properly appreciated it can
only be, I feel sure, because the juxtaposition of the words
mind, life and body has hitherto been assumed to provide
a theme for philosophers only and not one for scientists.
These observations suggest very convincingly that some
of the causes that constitute a change in organic substance
are not physical forces. It is very important to our understanding of many scientific facts to know whether this is
true or not. If it is we shall have to alter our conception
of causality quite radically. Hence this book. I want to
show that it is necessary, in the interests of scientific
progress, to apply scientific method to the following very
Does a complete list of the component causes of a physical
change necessarily contain only physical forces?
In that form the question is rather too general for
discussion in terms of concrete facts. And as it is only raised
by events in the organic world it can usefully be replaced
by two other, rather more specific, questions:
Do our non-material minds control our material bodies?
The answer "yes" to either of these two questions can
only mean that some of the causes of a physical change in
our bodies have a non-material origin. I shall show in due
course why, with such an origin, these causes cannot be
physical forces. To answer "yes" is, therefore, to deny the
hypothesis that all causes of a physical change are necessarily physical forces. And there are many who do answer
"yes", though I doubt whether they are aware of the
implications of their answer.
Common sense takes the answer "yes" for granted.
According to its judgement the power of thought is a
reality; there can be no doubt that our non-material
minds control our material actions. But then common
sense is a fallible instrument, as science has proved over
and over again.
The theologian will also answer at least the first question
with an unhesitating "yes". That mind controls body is
with him a matter of faith to which he will hardly admit
the possibility of doubt.
And the scientist? He is often influenced by common
sense and sometimes by theological considerations. He
may be inclined to answer "yes" until the implications of
that answer become apparent. Then he may reverse his
opinion. For the unproved assumption that all causes are
necessarily physical forces has become with many
scientists a matter of faith that will hardly admit the
possibility of doubt. But both the answer "yes" and the
answer "no" raises some formidable problems, as I shall
show later on, and a facile solution of these simply won't do.
So it would be a bold man who ventured to assert that as
much is known about causality as scientists need to know.
Let me add a few more basic questions to those already
formulated. They will help to define the scope of the
Active is the operative word here. For there are schools
of philosophy according to which mind and life, though
real, are not active; they are said to be no more than
convenient words with which to express the sum total of a
collection of attributes common to certain living things.
One of these schools declares that mind and life "emerge"
from the specific relatedness between the atoms that
constitute the living body. If adherents of these schools are
right it is wrong to say that mind and life control the
body, for a mere attribute cannot, of course, control
To distinguish attributes from active realities one would
I have to call them passive realities. An active reality can
do something; it can run, or fight, or eat or build things;
it can exercise choice; sometimes it can apply a force and
cause things to move. Anything that, by the common use
of language, can be called a cause must also be called an
active reality. But a mere attribute can do none of these
things; it is meaningless to speak of what it does; one can
only speak of what it is.
The answer depends, of course, on how the word
distinct is to be understood. It has been argued, perhaps
rightly, that our minds cannot exist without our bodies,
nor our bodies without our minds. From this interdependence one might assume, rather carelessly, that
they cannot be distinguished. But interdependence is not a
synonym for identity. In the above question distinct is to be
understood in the sense in which the head is distinct from
the trunk and also in the sense in which the driver is
distinct from the motor-car. They are distinct, even
I though the head cannot exist without the trunk or the
trunk without the head, just as the driver and the car
cannot each perform his or its proper function without the
other. Those who believe that mind and life are distinct
in this sense probably also believe that they both have a
controlling function. And those who believe that they are
not distinct in this sense will deny them any controlling
Are mind and life material or non-material?
The meaning of this question cannot be clear unless
the meaning of the words material and non-material has
first been defined; and this will not be done until the next
two chapters. However the common use of language
limits any possible uncertainty to some extent. It would
not conform to the common use of language to say that
mind and life were non-material if one thought of them
as tenuous fluids suffusing living tissues, as vitalist philosophers seem at one time to have done. If they were they
could be the origin of physical forces and there would
be no need to doubt the hypothesis that all causes are
physical forces. It is only if they are non-material in a
truer sense, in the sense that they cannot be the origin of
physical forces, that any doubt arises.
The more sophisticated among those who believe that
the mind controls the body do not think of it as a tenuous
fluid. They think of it as truly non-material. So they
believe that what is non-material can contribute to the
causes of material events. But it is just the more sophisticated, particularly if they. have some knowledge of
physics, who are also convinced that the only possible
causes of material events are physical forces. Hence they
believe that what is non-material can exert a physical
force. This belief, we shall find, is untenable. So those
who hold it must either revise their belief about the nature
of mind or their belief about the nature of causality. They
can retain the belief that the mind is a non-material
influence or they can retain their belief that all causes are
physical forces; but they cannot retain both beliefs.
I am afraid that they will not find the choice attractive.
But then scientific conclusions are not to be tested by the
criterion of attractiveness. That is the reason why laymen
sometimes disapprove of science.
Is the universe a monistic or a dualistic one?
This question has been debated by philosophers for a
long while. It is odd that those most concerned to understand the nature of causality, namely scientists, have contributed so little to the discussion. For the question has an
immediate bearing on the nature of causality. A monistic
universe is one in which matter, in the widest sense of the
I word, is the only active reality. In such a universe all
causes are physical forces. On the other hand part of a
dualistic universe is, by definition, distinct from matter.
This part is assumed also to influence the course of
events; so it is assumed to be a source of causes, causes
that are not physical forces. A dualist cannot accept the
hypothesis that all causes are physical forces.
If and when an integration of all knowledge has been achieved
will all the scences appear as branches of physics?
There is a sense in which chemistry now appears as a
branch of physics, for its laws are only special applications
of the laws of physics, of the laws according to which
matter acts on matter. If the universe is monistic all
laws are, in the same sense, special applications of the
laws-of physics; for all of them are laws that define the
way in which matter acts on matter. The laws of biology
and psychology must then be among these. But if the
universe is dualistic the laws according to which matter
acts on matter are not the only ones. There must be others
that could not, without unduly straining the use of language,
be described as laws of physics. The laws of biology and
psychology may, in that case be distinct from those of
The above eight questions are all basic and, though
they differ greatly in form, they hardly differ at all in
content. They all amount to much the same question,
they all have the same bearing, on the nature of causality,
and they all serve to distinguish between the monistic
and the dualistic views of reality. Those who would give
the monistic answer to one would give the monistic answer
to all; those who would give the dualistic answer to one
would give the dualistic answer to all; those who would
give an evasive answer to one would give an evasive answer
to all. And they are all questions to which no one with a
sense of responsibility ought to give a hasty answer,
though hasty answers are, unfortunately, all too frequent.
Nor are they questions to which philosophical method
is very appropriate. I say this although I am well aware
that philosophers have been debating them for several
centuries and that sundry rival schools have always
claimed to possess the key to the door behind which the
answers are to be found. But I am also aware that each
key unlocks a different door. After all those years of
intensive effort philosophical method has not produced
an agreed answer to a single one of the above eight questions. Perhaps it could do so after a few more centuries;
but scientists need to improve their understanding of
causality now. Where philosophical method has failed
scientific method is at least worth trying.
At this point it may be helpful, even at the risk of a. little
repetitiveness, to summarise very briefly the answers that
can be given to the above questions. The monistic answers
are that all causes are physical forces, that in so far as
mind and life are realities they are what I have called
passive realities, that they do not control the body but are
only manifestations of its structure and composition,
that they are not distinct from the body in the sense in
which the driver is distinct from his motor-car, that they
are in no sense of the word non-material influences, that
they cannot be called the causes of anything but rather
effects resulting from certain specific configurations. As
monists believe that the universe consists only of what,
sufficiently widely defined, is called matter, they would
also say that physics, being the study of matter in all its
aspects, will some day embrace all the other sciences.
The dualistic answers are every time the exact opposites
of these. Though answers have occasionally been
attempted as a compromise between the extreme opposites,
none of them will bear criticism. When an attempt is
made to answer one of the eight questions in one sense
and another in the opposite sense the inconsistency is
glaring. And those compromise answers that claim to say
neither yes nor no but something between these simple
alternatives are meaningless. What they really do, I have
noticed, is either to dodge the questions and answer
others instead or to be so verbose, obscure and confusing
that they might mean anything.
One of the unpleasant truths that have to be faced is
that both sets of answers, the monistic and the dualistic
ones, raise formidable difficulties. The pillars that support
the roof of monism and those that support the roof of
dualism appear, on close examination, to be equally
insecure. Only painstaking scientific study can reveal
which are really the strong ones. And this is why so few,
even among scientists, have the patience to consider the
objections to their favoured doctrine. Whether they find
their spiritual home under the monistic or the dualistic
roof, they are, unknown to themselves, apprehensive of
the safety of the pillars that support it; they dare not allow
those pillars to be shaken lest they should collapse. Such
is, after all, human nature.
In this book I have set myself the unpopular task of
attempting to shake all the pillars. I shall begin in
Chapter VII with those that support the dualistic roof.
I shall try to show how justified those seem to be who
declare that monistic answers to the eight questions are
the only tenable ones. Later on I shall attack the pillars
that support the roof of monism with equal ruthlessness.
I shall show that they depend for their apparent stability
on the ignoring of many facts that every one knows to be
And the net result? Will it be the conclusion that both
roofs must collapse on us when their pillars are shaken by
criticism? Must we resign ourselves to one of those
compromises between yes and no with all their verbosities,
their obscurities, their ambiguities? I do not think so.
If I may try to announce in a few words a conclusion
that will only be reached after much ground has been
laboriously covered, it is this. We shall find that the
pillars supporting the monistic roof look comparatively
strong. But we shall also find on closer examination that
the pillars supporting the monistic roof are, nevertheless,
quite unequal to their duty, and that there is a reasonable
prospect that those supporting the .dualistic roof are
really stronger than they seem to be, so strong that they
can withstand the severest criticism.
Let us now leave metaphor and tackle the hard facts
on which alone it can be decided whether science will,
in future, take causes into consideration that are not
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