The case, then, stands thus: a certain group of disciplines is regarded
as falling peculiarly within the province of the professor of
philosophy, and the sciences which constitute it are frequently called
the philosophical sciences; moreover, it is regarded as quite proper
that the teacher of philosophy should concern himself with the problems
of religion, and should pry into the methods and fundamental
assumptions of special sciences in all of which it is impossible that
he should be an adept. The question naturally arises: Why has his task
come to be circumscribed as it is? Why should he teach just these
things and no others?
To this question certain persons are at once ready to give an answer.
There was a time, they argue, when it seemed possible for one man to
embrace the whole field of human knowledge. But human knowledge grew;
the special sciences were born; each concerned itself with a definite
class of facts and developed its own methods. It became possible and
necessary for a man to be, not a scientist at large, but a chemist, a
physicist, a biologist, an economist. But in certain portions of the
great field men have met with peculiar difficulties; here it cannot be
said that we have sciences, but rather that we have attempts at
science. The philosopher is the man to whom is committed what is left
when we have taken away what has been definitely established or is
undergoing investigation according to approved scientific methods. He
is Lord of the Uncleared Ground, and may wander through it in his
compassless, irresponsible way, never feeling that he is lost, for he
has never had any definite bearings to lose.
Those who argue in this way support their case by pointing to the lack
of a general consensus of opinion which obtains in many parts of the
field which the philosopher regards as his own; and also by pointing
out that, even within this field, there is a growing tendency on the
part of certain sciences to separate themselves from philosophy and
become independent. Thus the psychologist and the logician are
sometimes very anxious to have it understood that they belong among the
scientists and not among the philosophers.
Now, this answer to the question that we have raised undoubtedly
contains some truth. As we have seen from the sketch contained in the
preceding pages, the word philosophy was once a synonym for the whole
sum of the sciences or what stood for such; gradually the several
sciences have become independent and the field of the philosopher has
been circumscribed. We must admit, moreover, that there is to be found
in a number of the special sciences a body of accepted facts which is
without its analogue in philosophy. In much of his work the
philosopher certainly seems to be walking upon more uncertain ground
than his neighbors; and if he is unaware of that fact, it must be
either because he has not a very nice sense of what constitutes
scientific evidence, or because he is carried away by his enthusiasm
for some particular form of doctrine.
Nevertheless, it is just to maintain that the answer we are discussing
is not a satisfactory one. For one thing, we find in it no indication
of the reason why the particular group of disciplines with which the
philosopher occupies himself has been left to him, when so many
sciences have announced their independence. Why have not these, also,
separated off and set up for themselves? Is it more difficult to work
in these fields than in others? and, if so, what reason can be assigned
for the fact?
Take psychology as an instance. How does it happen that the physicist
calmly develops his doctrine without finding it necessary to make his
bow to philosophy at all, while the psychologist is at pains to explain
that his book is to treat psychology as "a natural science," and will
avoid metaphysics as much as possible? For centuries men have been
interested in the phenomena of the human mind. Can anything be more
open to observation than what passes in a man's own consciousness?
Why, then, should the science of psychology lag behind? and why these
endless disputes as to whether it can really be treated as a "natural
science" at all?
Again. May we assume that, because certain disciplines have taken a
position of relative independence, therefore all the rest of the field
will surely come to be divided up in the same way, and that there will
be many special sciences, but no such thing as philosophy? It is hasty
to assume this on no better evidence than that which has so far been
presented. Before making up one's mind upon this point, one should
take a careful look at the problems with which the philosopher occupies
himself.
A complete answer to the questions raised above can only be given in
the course of the book, where the main problems of philosophy are
discussed, and the several philosophical sciences are taken up and
examined. But I may say, in anticipation, as much as this:--
(1) Philosophy is reflective knowledge. What is meant by reflective
knowledge will be explained at length in the next chapter.
(2) The sciences which are grouped together as philosophical are those
in which we are forced back upon the problems of reflective thought,
and cannot simply put them aside.
(3) The peculiar difficulties of reflective thought may account for the
fact that these sciences are, more than others, a field in which we may
expect to find disputes and differences of opinion.
(4) We need not be afraid that the whole field of human knowledge will
come to be so divided up into special sciences that philosophy will
disappear. The problems with which the philosopher occupies himself
are real problems, which present themselves unavoidably to the
thoughtful mind, and it is not convenient to divide these up among the
several sciences. This will become clearer as we proceed.
[1] "First Principles," Part II, section 37.
CHAPTER II
COMMON THOUGHT, SCIENCE, AND REFLECTIVE THOUGHT
7. COMMON THOUGHT.--Those who have given little attention to the study
of the human mind are apt to suppose that, when the infant opens its
eyes upon the new world of objects surrounding its small body, it sees
things much as they do themselves. They are ready to admit that it
does not know much _about_ things, but it strikes them as absurd for
any one to go so far as to say that it does not see things--the things
out there in space before its eyes.
Nevertheless, the psychologist tells us that it requires quite a course
of education to enable us to see things--not to have vague and
unmeaning sensations, but to see things, things that are known to be
touchable as well as seeable, things that are recognized as having size
and shape and position in space. And he aims a still severer blow at
our respect for the infant when he goes on to inform us that the little
creature is as ignorant of itself as it is of things; that in its small
world of as yet unorganized experiences there is no self that is
distinguished from other things; that it may cry vociferously without
knowing who is uncomfortable, and may stop its noise without knowing
who has been taken up into the nurse's arms and has experienced an
agreeable change.
This chaotic little world of the dawning life is not our world, the
world of common thought, the world in which we all live and move in
maturer years; nor can we go back to it on the wings of memory. We
seem to ourselves to have always lived in a world of things,--things in
time and space, material things. Among these things there is one of
peculiar interest, and which we have not placed upon a par with the
rest, our own body, which sees, tastes, touches, other things. We
cannot remember a time when we did not know that with this body are
somehow bound up many experiences which interest us acutely; for
example, experiences of pleasure and pain. Moreover, we seem always to
have known that certain of the bodies which surround our own rather
resemble our own, and are in important particulars to be distinguished
from the general mass of bodies.
Thus, we seem always to have been living in a world of _things_ and to
have recognized in that world the existence of ourselves and of other
people. When we now think of "ourselves" and of "other people," we
think of each of the objects referred to as possessing a _mind_. May
we say that, as far back as we can remember, we have thought of
ourselves and of other persons as possessing minds?
Hardly. The young child does not seem to distinguish between mind and
body, and, in the vague and fragmentary pictures which come back to us
from our early life, certainly this distinction does not stand out.
The child may be the completest of egoists, it may be absorbed in
itself and all that directly concerns this particular self, and yet it
may make no conscious distinction between a bodily self and a mental,
between mind and body. It does not explicitly recognize its world as a
world that contains minds as well as bodies.
But, however it may be with the child in the earlier stages of its
development, we must all admit that the mature man does consciously
recognize that the world in which he finds himself is a world that
contains minds as well as bodies. It never occurs to him to doubt that
there are bodies, and it never occurs to him to doubt that there are
minds.
Does he not perceive that he has a body and a mind? Has he not
abundant evidence that his mind is intimately related to his body?
When he shuts his eyes, he no longer sees, and when he stops his ears,
he no longer hears; when his body is bruised, he feels pain; when he
wills to raise his hand, his body carries out the mental decree. Other
men act very much as he does; they walk and they talk, they laugh and
they cry, they work and they play, just as he does. In short, they act
precisely as though they had minds like his own. What more natural
than to assume that, as he himself gives expression, by the actions of
his body, to the thoughts and emotions in his mind, so his neighbor
does the same?
We must not allow ourselves to underrate the plain man's knowledge
either of bodies or of minds. It seems, when one reflects upon it, a
sufficiently wonderful thing that a few fragmentary sensations should
automatically receive an interpretation which conjures up before the
mind a world of real things; that, for example, the little patch of
color sensation which I experience when I turn my eyes toward the
window should seem to introduce me at once to a world of material
objects lying in space, clearly defined in magnitude, distance, and
direction; that an experience no more complex should be the key which
should unlock for me the secret storehouse of another mind, and lay
before me a wealth of thoughts and emotions not my own. From the poor,
bare, meaningless world of the dawning intelligence to the world of
common thought, a world in which real things with their manifold
properties, things material and things mental, bear their part, is
indeed a long step.
And we should never forget that he who would go farther, he who would
strive to gain a better knowledge of matter and of mind by the aid of
science and of philosophical reflection, must begin his labors on this
foundation which is common to us all. How else can he begin than by
accepting and more critically examining the world as it seems revealed
in the experience of the race?
8. SCIENTIFIC KNOWLEDGE.--Still, the knowledge of the world which we
have been discussing is rather indefinite, inaccurate, and
unsystematic. It is a sufficient guide for common life, but its
deficiencies may be made apparent. He who wishes to know matter and
mind better cannot afford to neglect the sciences.
Now, it is important to observe that although, when the plain man grows
scientific, great changes take place in his knowledge of things, yet
his way of looking at the mind and the world remains in general much
what it was before. To prevent this statement from being
misunderstood, I must explain it at some length.
Let us suppose that the man in question takes up the study of botany.
Need he do anything very different from what is done more imperfectly
by every intelligent man who interests himself in plants? There in the
real material world before him are the same plants that he observed
somewhat carelessly before. He must collect his information more
systematically and must arrange it more critically, but his task is not
so much to do something different as it is to do the same thing much
better.
The same is evidently true of various other sciences, such as geology,
zoology, physiology, sociology. Some men have much accurate
information regarding rocks, animals, the functions of the bodily
organs, the development of a given form of society, and other things of
the sort, and other men have but little; and yet it is usually not
difficult for the man who knows much to make the man who knows little
understand, at least, what he is talking about. He is busying himself
with _things_--the same things that interest the plain man, and of
which the plain man knows something. He has collected information
touching their properties, their changes, their relationships; but to
him, as to his less scientific neighbor, they are the same things they
always were,--things that he has known from the days of childhood.
Perhaps it will be admitted that this is true of such sciences as those
above indicated, but doubted whether it is true of all the sciences,
even of all the sciences which are directly concerned with _things_ of
_some_ sort. For example, to the plain man the world of material
things consists of things that can be seen and touched. Many of these
seem to fill space continuously. They may be divided, but the parts
into which they may be divided are conceived as fragments of the
things, and as of the same general nature as the wholes of which they
are parts. Yet the chemist and the physicist tell us that these same
extended things are not really continuous, as they seem to us to be,
but consist of swarms of imperceptible atoms, in rapid motion, at
considerable distances from one another in space, and grouped in
various ways.
What has now become of the world of realities to which the plain man
pinned his faith? It has come to be looked upon as a world of
appearances, of phenomena, of manifestations, under which the real
things, themselves imperceptible, make their presence evident to our
senses. Is this new, real world the world of things in which the plain
man finds himself, and in which he has felt so much at home?
A closer scrutiny reveals that the world of atoms and molecules into
which the man of science resolves the system of material things is not,
after all, so very different in kind from the world to which the plain
man is accustomed. He can understand without difficulty the language
in which it is described to him, and he can readily see how a man may
be led to assume its existence.
The atom is not, it is true, directly perceivable by sense, but it is
conceived as though it and its motions were thus perceivable. The
plain man has long known that things consist of parts which remain,
under some circumstances, invisible. When he approaches an object from
a distance, he sees parts which he could not see before; and what
appears to the naked eye a mere speck without perceptible parts is
found under the microscope to be an insect with its full complement of
members. Moreover, he has often observed that objects which appear
continuous when seen from a distance are evidently far from continuous
when seen close at hand. As we walk toward a tree we can see the
indefinite mass of color break up into discontinuous patches; a fabric,
which presents the appearance of an unbroken surface when viewed in
certain ways may be seen to be riddled with holes when held between the
eye and the light. There is no man who has not some acquaintance with
the distinction between appearance and reality, and who does not make
use of the distinction in common life.
Nor can it seem a surprising fact that different combinations of atoms
should exhibit different properties. Have we not always known that
things in combination are apt to have different properties from the
same things taken separately? He who does not know so much as this is
not fit even to be a cook.
No, the imperceptible world of atoms and molecules is not by any means
totally different from the world of things in which the plain man
lives. These little objects and groups of objects are discussed very
much as we discuss the larger objects and groups of objects to which we
are accustomed. We are still concerned with _things_ which exist in
space and move about in space; and even if these things are small and
are not very familiarly known, no intellectual revolution is demanded
to enable a man to understand the words of the scientist who is talking
about them, and to understand as well the sort of reasonings upon which
the doctrine is based.
9. MATHEMATICS.--Let us now turn to take a glance at the mathematical
sciences. Of course, these have to do with things sooner or later, for
our mathematical reasonings would be absolutely useless to us if they
could not be applied to the world of things; but in mathematical
reasonings we abstract from things for the time being, confident that
we can come back to them when we want to do so, and can make use of the
results obtained in our operations.
Now, every civilized man who is not mentally deficient can perform the
fundamental operations of arithmetic. He can add and subtract,
multiply and divide. In other words, he can use _numbers_. The man
who has become an accomplished mathematician can use numbers much
better; but if we are capable of following intelligently the intricate
series of operations that he carries out on the paper before us, and
can see the significance of the system of signs which he uses as an
aid, we shall realize that he is only doing in more complicated ways
what we have been accustomed to do almost from our childhood.
If we are interested, not so much in performing the operations, as in
inquiring into what really takes place in a mind when several units are
grasped together and made into a new unit,--for example, when twelve
units are thought as one dozen,--the mathematician has a right to say:
I leave all that to the psychologist or to the metaphysician; every one
knows in a general way what is meant by a unit, and knows that units
can be added and subtracted, grouped and separated; I only undertake to
show how one may avoid error in doing these things.
It is with geometry as it is with arithmetic. No man is wholly
ignorant of points, lines, surfaces, and solids. We are all aware that
a short line is not a point, a narrow surface is not a line, and a thin
solid is not a mere surface. A door so thin as to have only one side
would be repudiated by every man of sense as a monstrosity. When the
geometrician defines for us the point, the line, the surface, and the
solid, and when he sets before us an array of axioms, or self-evident
truths, we follow him with confidence because he seems to be telling us
things that we can directly see to be reasonable; indeed, to be telling
us things that we have always known.
The truth is that the geometrician does not introduce us to a new world
at all. He merely gives us a fuller and a more exact account than was
before within our reach of the space relations which obtain in the
world of external objects, a world we already know pretty well.
Suppose that we say to him: You have spent many years in dividing up
space and in scrutinizing the relations that are to be discovered in
that realm; now tell us, what is space? Is it real? Is it a thing, or
a quality of a thing, or merely a relation between things? And how can
any man think space, when the ideas through which he must think it are
supposed to be themselves non-extended? The space itself is not
supposed to be in the mind; how can a collection of non-extended ideas
give any inkling of what is meant by extension?
Would any teacher of mathematics dream of discussing these questions
with his class before proceeding to the proof of his propositions? It
is generally admitted that, if such questions are to be answered at
all, it is not with the aid of geometrical reasonings that they will be
answered.
10. THE SCIENCE OF PSYCHOLOGY.--Now let us come back to a science which
has to do directly with things. We have seen that the plain man has
some knowledge of minds as well as of material things. Every one
admits that the psychologist knows minds better. May we say that his
knowledge of minds differs from that of the plain man about as the
knowledge of plants possessed by the botanist differs from that of all
intelligent persons who have cared to notice them? Or is it a
knowledge of a quite different kind?
Those who are familiar with the development of the sciences within
recent years have had occasion to remark the fact that psychology has
been coming more and more to take its place as an independent science.
Formerly it was regarded as part of the duty of the philosopher to
treat of the mind and its knowledge; but the psychologist who pretends
to be no more than a psychologist is a product of recent times. This
tendency toward specialization is a natural thing, and is quite in line
with what has taken place in other fields of investigation.
When any science becomes an independent discipline, it is recognized
that it is a more or less limited field in which work of a certain kind
is done in a certain way. Other fields and other kinds of work are to
some extent ignored. But it is quite to be expected that there should
be some dispute, especially at first, as to what does or does not
properly fall within the limits of a given science. Where these limits
shall be placed is, after all, a matter of convenience; and sometimes
it is not well to be too strict in marking off one field from another.
It is well to watch the actual development of a science, and to note
the direction instinctively taken by investigators in that particular
field.
If we compare the psychology of a generation or so ago with that of the
present day, we cannot but be struck with the fact that there is an
increasing tendency to treat psychology as a _natural science_. By
this is not meant, of course, that there is no difference between
psychology and the sciences that concern themselves with the world of
material things--psychology has to do primarily with minds and not with
bodies. But it is meant that, as the other sciences improve upon the
knowledge of the plain man without wholly recasting it, as they accept
the world in which he finds himself and merely attempt to give us a
better account of it, so the psychologist may accept the world of
matter and of minds recognized by common thought, and may devote
himself to the study of minds, without attempting to solve a class of
problems discussed by the metaphysician. For example, he may refuse to
discuss the question whether the mind can really know that there is an
external world with which it stands in relation, and from which it
receives messages along the avenues of the senses. He may claim that
it is no more his business to treat of this than it is the business of
the mathematician to treat of the ultimate nature of space.
Thus the psychologist assumes without question the existence of an
external real world, a world of matter and motion. He finds in this
world certain organized bodies that present phenomena which he regards
as indicative of the presence of minds. He accepts it as a fact that
each mind knows its own states directly, and knows everything else by
inference from those states, receiving messages from the outer world
along one set of nerves and reacting along another set. He conceives
of minds as wholly dependent upon messages thus conveyed to them from
without. He tells us how a mind, by the aid of such messages,
gradually builds up for itself the notion of the external world and of
the other minds which are connected with bodies to be found in that
world.
We may fairly say that all this is merely a development of and an
improvement upon the plain man's knowledge of minds and of bodies.
There is no normal man who does not know that his mind is more
intimately related to his body than it is to other bodies. We all
distinguish between our ideas of things and the external things they
represent, and we believe that our knowledge of things comes to us
through the avenues of the senses. Must we not open our eyes to see,
and unstop our ears to hear? We all know that we do not perceive other
minds directly, but must infer their contents from what takes place in
the bodies to which they are referred--from words and actions.
Moreover, we know that a knowledge of the outer world and of other
minds is built up gradually, and we never think of an infant as knowing
what a man knows, much as we are inclined to overrate the minds of
infants.
The fact that the plain man and the psychologist do not greatly differ
in their point of view must impress every one who is charged with the
task of introducing students to the study of psychology and philosophy.
It is rather an easy thing to make them follow the reasonings of the
psychologist, so long as he avoids metaphysical reflections. The
assumptions which he makes seem to them not unreasonable; and, as for
his methods of investigation, there is no one of them which they have
not already employed themselves in a more or less blundering way. They
have had recourse to _introspection_, _i.e._ they have noticed the
phenomena of their own minds; they have made use of the _objective
method_, i.e. they have observed the signs of mind exhibited by other
persons and by the brutes; they have sometimes _experimented_--this is
done by the schoolgirl who tries to find out how best to tease her
roommate, and by the boy who covers and uncovers his ears in church to
make the preacher sing a tune.
It may not be easy to make men good psychologists, but it is certainly
not difficult to make them understand what the psychologist is doing
and to make them realize the value of his work. He, like the workers
in the other natural sciences, takes for granted the world of the plain
man, the world of material things in space and time and of minds
related to those material things. But when it is a question of
introducing the student to the reflections of the philosophers the case
is very different. We seem to be enticing him into a new and a strange
world, and he is apt to be filled with suspicion and distrust. The
most familiar things take on an unfamiliar aspect, and questions are
raised which it strikes the unreflective man as highly absurd even to
propose. Of this world of reflective thought I shall say just a word
in what follows.
11. REFLECTIVE THOUGHT.--If we ask our neighbor to meet us somewhere at
a given hour, he has no difficulty in understanding what we have
requested him to do. If he wishes to do so, he can be on the spot at
the proper moment. He may never have asked himself in his whole life
what he means by space and by time. He may be quite ignorant that
thoughtful men have disputed concerning the nature of these for
centuries past.
And a man may go through the world avoiding disaster year after year by
distinguishing with some success between what is real and what is not
real, and yet he may be quite unable to tell us what, in general, it
means for a thing to be real. Some things are real and some are not;
as a rule he seems to be able to discover the difference; of his method
of procedure he has never tried to give an account to himself.
That he has a mind he cannot doubt, and he has some idea of the
difference between it and certain other minds; but even the most ardent
champion of the plain man must admit that he has the most hazy of
notions touching the nature of his mind. He seems to be more doubtful
concerning the nature of the mind and its knowledge than he is
concerning the nature of external things. Certainly he appears to be
more willing to admit his ignorance in this realm.
And yet the man can hold his own in the world of real things. He can
distinguish between this thing and that, this place and that, this time
and that. He can think out a plan and carry it into execution; he can
guess at the contents of other minds and allow this knowledge to find
its place in his plan.
All of which proves that our knowledge is not necessarily useless
because it is rather dim and vague. It is one thing to use a mental
state; it is another to have a clear comprehension of just what it is
and of what elements it may be made up. The plain man does much of his
thinking as we all tie our shoes and button our buttons. It would be
difficult for us to describe these operations, but we may perform them
very easily nevertheless. When we say that we _know_ how to tie our
shoes, we only mean that we can tie them.
Now, enough has been said in the preceding sections to make clear that
the vagueness which characterizes many notions which constantly recur
in common thought is not wholly dispelled by the study of the several
sciences. The man of science, like the plain man, may be able to use
very well for certain purposes concepts which he is not able to analyze
satisfactorily. For example, he speaks of space and time, cause and
effect, substance and qualities, matter and mind, reality and
unreality. He certainly is in a position to add to our knowledge of
the things covered by these terms. But we should never overlook the
fact that the new knowledge which he gives us is a knowledge of the
same kind as that which we had before. He measures for us spaces and
times; he does not tell us what space and time are. He points out the
causes of a multitude of occurrences; he does not tell us what we mean
whenever we use the word "cause." He informs us what we should accept
as real and what we should repudiate as unreal; he does not try to show
us what it is to be real and what it is to be unreal.
In other words, the man of science _extends_ our knowledge and makes it
more accurate; he does not _analyze_ certain fundamental conceptions,
which we all use, but of which we can usually give a very poor account.
On the other hand, it is the task of _reflective thought_, not in the
first instance, to extend the limits of our knowledge of the world of
matter and of minds, but rather _to make us more clearly conscious of
what that knowledge really is_. Philosophical reflection takes up and
tries to analyze complex thoughts that men use daily without caring to
analyze them, indeed, without even realizing that they may be subjected
to analysis.
It is to be expected that it should impress many of those who are
introduced to it for the first time as rather a fantastic creation of
problems that do not present themselves naturally to the healthy mind.
There is no thoughtful man who does not reflect sometimes and about
some things; but there are few who feel impelled to go over the whole
edifice of their knowledge and examine it with a critical eye from its
turrets to its foundations. In a sense, we may say that philosophical
thought is not natural, for he who is examining the assumptions upon
which all our ordinary thought about the world rests is no longer in
the world of the plain man. He is treating things as men do not
commonly treat them, and it is perhaps natural that it should appear to
some that, in the solvent which he uses, the real world in which we all
rejoice should seem to dissolve and disappear.
I have said that it is not the task of reflective thought, _in the
first instance_, to extend the limits of our knowledge of the world of
matter and of minds. This is true. But this does not mean that, as a
result of a careful reflective analysis, some errors which may creep
into the thought both of the plain man and of the scientist may not be
exploded; nor does it mean that some new extensions of our knowledge
may not be suggested.
In the chapters to follow I shall take up and examine some of the
problems of reflective thought. And I shall consider first those
problems that present themselves to those who try to subject to a
careful scrutiny our knowledge of the external world. It is well to
begin with this, for, even in our common experience, it seems to be
revealed that the knowledge of material things is a something less
vague and indefinite than the knowledge of minds.
II. PROBLEMS TOUCHING THE EXTERNAL WORLD
CHAPTER III
IS THERE AN EXTERNAL WORLD?
12. HOW THE PLAIN MAN THINKS HE KNOWS THE WORLD.--As schoolboys we
enjoyed Cicero's joke at the expense of the "minute philosophers."
They denied the immortality of the soul; he affirmed it; and he
congratulated himself upon the fact that, if they were right, they
would not survive to discover it and to triumph over him.
At the close of the seventeenth century the philosopher John Locke was
guilty of a joke of somewhat the same kind. "I think," said he,
"nobody can, in earnest, be so skeptical as to be uncertain of the
existence of those things which he sees and feels. At least, he that
can doubt so far (whatever he may have with his own thoughts) will
never have any controversy with me; since he can never be sure I say
anything contrary to his own opinion."
Now, in this chapter and in certain chapters to follow, I am going to
take up and turn over, so that we may get a good look at them, some of
the problems that have presented themselves to those who have reflected
upon the world and the mind as they seem given in our experience. I
shall begin by asking whether it is not possible to doubt that there is
an external world at all.
The question cannot best be answered by a jest. It may, of course, be
absurd to maintain that there is no external world; but surely he, too,
is in an absurd position who maintains dogmatically that there is one,
and is yet quite unable to find any flaw in the reasonings of the man
who seems to be able to show that this belief has no solid foundation.
And we must not forget that the men who have thought it worth while to
raise just such questions as this, during the last twenty centuries,
have been among the most brilliant intellects of the race. We must not
assume too hastily that they have occupied themselves with mere
trivialities.
Since, therefore, so many thoughtful men have found it worth while to
ask themselves seriously whether there is an external world, or, at
least, how we can know that there is an external world, it is not
unreasonable to expect that, by looking for it, we may find in our
common experience or in science some difficulty sufficient to suggest
the doubt which at first strikes the average man as preposterous. In
what can such a doubt take its rise? Let us see.
I think it is scarcely too much to say that the plain man believes that
he _does not_ directly perceive an external world, and that he, at the
same time, believes that he _does_ directly perceive one. It is quite
possible to believe contradictory things, when one's thought of them is
somewhat vague, and when one does not consciously bring them together.
As to the first-mentioned belief. Does not the plain man distinguish
between his ideas of things and the things themselves? Does he not
believe that his ideas come to him through the avenues of the senses?
Is he not aware of the fact that, when a sense is disordered, the thing
as he perceives it is not like the thing "as it is"? A blind man does
not see things when they are there; a color-blind man sees them as
others do not see them; a man suffering under certain abnormal
conditions of the nervous system sees things when they are not there at
all, _i.e._ he has hallucinations. The thing itself, as it seems, is
not in the man's mind; it is the idea that is in the man's mind, and
that represents the thing. Sometimes it appears to give a true account
of it; sometimes it seems to give a garbled account; sometimes it is a
false representative throughout--there is no reality behind it. It is,
then, the _idea_ that is immediately known, and not the _thing_; the
thing is merely _inferred_ to exist.
I do not mean to say that the plain man is conscious of drawing this
conclusion. I only maintain that it seems a natural conclusion to draw
from the facts which he recognizes, and that sometimes he seems to draw
the conclusion half-consciously.
On the other hand, we must all admit that when the plain man is not
thinking about the distinction between ideas and things, but is looking
at some material object before him, is touching it with his fingers and
turning it about to get a good look at it, it never occurs to him that
he is not directly conscious of the thing itself.
He seems to himself to perceive the thing immediately; to perceive it
_as_ it is and _where_ it is; to perceive it as a really extended
thing, out there in space before his body. He does not think of
himself as occupied with mere images, representations of the object.
He may be willing to admit that his mind is in his head, but he cannot
think that what he sees is in his head. Is not the object _there_?
does he not _see_ and _feel_ it? Why doubt such evidence as this? He
who tells him that the external world does not exist seems to be
denying what is immediately given in his experience.
The man who looks at things in this way assumes, of course, that the
external object is known directly, and is not a something merely
inferred to exist from the presence of a representative image. May one
embrace this belief and abandon the other one? If we elect to do this,
we appear to be in difficulties at once. All the considerations which
made us distinguish so carefully between our ideas of things and the
things themselves crowd in upon us. Can it be that we know things
independently of the avenues of the senses? Would a man with different
senses know things just as we do? How can any man suffer from an
hallucination, if things are not inferred from images, but are known
independently?
The difficulties encountered appear sufficiently serious even if we
keep to that knowledge of things which seems to be given in common
experience. But even the plain man has heard of atoms and molecules;
and if he accepts the extension of knowledge offered him by the man of
science, he must admit that, whatever this apparently immediately
perceived external thing may be, it cannot be the external thing that
science assures him is out there in space beyond his body, and which
must be a very different sort of thing from the thing he seems to
perceive. The thing he perceives must, then, be _appearance_; and
where can that appearance be if not in his own mind?
The man who has made no study of philosophy at all does not usually
think these things out; but surely there are interrogation marks
written up all over his experience, and he misses them only because he
does not see clearly. By judiciously asking questions one may often
lead him either to affirm or to deny that he has an immediate knowledge
of the external world, pretty much as one pleases. If he affirms it,
his position does not seem to be a wholly satisfactory one, as we have
seen; and if he denies it, he makes the existence of the external world
wholly a matter of inference from the presence of ideas in the mind,
and he must stand ready to justify this inference.
To many men it has seemed that the inference is not an easy one to
justify. One may say: We could have no ideas of things, no sensations,
if real things did not exist and make an impression upon our senses.
But to this it may be answered: How is that statement to be proved? Is
it to be proved by observing that, when things are present and affect
the senses, there come into being ideas which represent the things?
Evidently such a proof as this is out of the question, for, if it is
true that we know external things only by inference and never
immediately, then we can never prove by observation that ideas and
things are thus connected. And if it is not to be proved by
observation, how shall it be proved? Shall we just assume it
dogmatically and pass on to something else? Surely there is enough in
the experience of the plain man to justify him in raising the question
whether he can certainly know that there is an external world.
13. THE PSYCHOLOGIST AND THE EXTERNAL WORLD.--We have seen just above
that the doubt regarding the existence of the world seems to have its
root in the familiar distinction between ideas and things, appearances
and the realities which they are supposed to represent. The
psychologist has much to say about ideas; and if sharpening and making
clear this distinction has anything to do with stirring up doubts, it
is natural to suppose that they should become more insistent when one
has exchanged the ignorance of everyday life for the knowledge of the
psychologist.
Now, when the psychologist asks how a given mind comes to have a
knowledge of any external thing, he finds his answer in the messages
which have been brought to the mind by means of the bodily senses. He
describes the sense-organs and the nervous connections between these
and the brain, and tells us that when certain nervous impulses have
traveled, let us say, from the eye or the ear to the brain, one has
sensations of sight or sound.
He describes for us in detail how, out of such sensations and the
memories of such sensations, we frame mental images of external things.
Between the mental image and the thing that it represents he
distinguishes sharply, and he informs us that the mind knows no more
about the external thing than is contained in such images. That a
thing is present can be known only by the fact that a message from the
thing is sent along the nerves, and what the thing is must be
determined from the character of the message. Given the image in the
absence of the thing,--that is to say, an hallucination,--the mind will
naturally suppose that the thing is present. This false supposition
cannot be corrected by a direct inspection of the thing, for such a
direct inspection of things is out of the question. The only way in
which the mind concerned can discover that the thing is absent is by
referring to its other experiences. This image is compared with other
images and is discovered to be in some way abnormal. We decide that it
is a false representative and has no corresponding reality behind it.
This doctrine taken as it stands seems to cut the mind off from the
external world very completely; and the most curious thing about it is
that it seems to be built up on the assumption that it is not really
true. How can one know certainly that there is a world of material
things, including human bodies with their sense-organs and nerves, if
no mind has ever been able to inspect directly anything of the sort?
How can we tell that a sensation arises when a nervous impulse has been
carried along a sensory nerve and has reached the brain, if every mind
is shut up to the charmed circle of its own ideas? The anatomist and
the physiologist give us very detailed accounts of the sense-organs and
of the brain; the physiologist even undertakes to measure the speed
with which the impulse passes along a nerve; the psychologist accepts
and uses the results of their labors. But can all this be done in the
absence of any first-hand knowledge of the things of which one is
talking? Remember that, if the psychologist is right, any external
object, eye, ear, nerve, or brain, which we can perceive directly, is a
mental complex, a something in the mind and not external at all. How
shall we prove that there are objects, ears, eyes, nerves, and
brains,--in short, all the requisite mechanism for the calling into
existence of sensations,--in an outer world which is not immediately
perceived but is only inferred to exist?
I do not wish to be regarded as impugning the right of the psychologist
to make the assumptions which he does, and to work as he does. He has
a right to assume, with the plain man, that there is an external world
and that we know it. But a very little reflection must make it
manifest that he seems, at least, to be guilty of an inconsistency, and
that he who wishes to think clearly should strive to see just where the
trouble lies.
So much, at least, is evident: the man who is inclined to doubt whether
there is, after all, any real external world, appears to find in the
psychologist's distinction between ideas and things something like an
excuse for his doubt. To get to the bottom of the matter and to
dissipate his doubt one has to go rather deeply into metaphysics. I
merely wish to show just here that the doubt is not a gratuitous one,
but is really suggested to the thoughtful mind by a reflection upon our
experience of things. And, as we are all apt to think that the man of
science is less given to busying himself with useless subtleties than
is the philosopher, I shall, before closing this chapter, present some
paragraphs upon the subject from the pen of a professor of mathematics
and mechanics.
14. THE "TELEPHONE EXCHANGE."--"We are accustomed to talk," writes
Professor Karl Pearson,[1] "of the 'external world,' of the 'reality'
outside us. We speak of individual objects having an existence
independent of our own. The store of past sense-impressions, our
thoughts and memories, although most probably they have beside their
psychical element a close correspondence with some physical change or
impress in the brain, are yet spoken of as _inside_ ourselves. On the
other hand, although if a sensory nerve be divided anywhere short of
the brain, we lose the corresponding class of sense impression, we yet
speak of many sense-impressions, such as form and texture, as existing
outside ourselves. How close then can we actually get to this supposed
world outside ourselves? Just as near but no nearer than the brain
terminals of the sensory nerves. We are like the clerk in the central
telephone exchange who cannot get nearer to his customers than his end
of the telephone wires. We are indeed worse off than the clerk, for to
carry out the analogy properly we must suppose him _never to have been
outside the telephone exchange, never to have seen a customer or any
one like a customer--in short, never, except through the telephone
wire, to have come in contact with the outside universe_. Of that
'real' universe outside himself he would be able to form no direct
impression; the real universe for him would be the aggregate of his
constructs from the messages which were caused by the telephone wires
in his office. About those messages and the ideas raised in his mind
by them he might reason and draw his inferences; and his conclusions
would be correct--for what? For the world of telephonic messages, for
the type of messages that go through the telephone. Something definite
and valuable he might know with regard to the spheres of action and of
thought of his telephonic subscribers, but outside those spheres he
could have no experience. Pent up in his office he could never have
seen or touched even a telephonic subscriber _in himself_. Very much
in the position of such a telephone clerk is the conscious _ego_ of
each one of us seated at the brain terminals of the sensory nerves.
Not a step nearer than those terminals can the _ego_ get to the 'outer
world,' and what in and for themselves are the subscribers to its nerve
exchange it has no means of ascertaining. Messages in the form of
sense-impressions come flowing in from that 'outside world,' and these
we analyze, classify, store up, and reason about. But of the nature of 'things-in-themselves,' of what may exist at the other end of our system of telephone wires, we know nothing at all. |
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