SENSATIONS AND "THINGS"
15. SENSE AND IMAGINATION.--Every one distinguishes between things
perceived and things only imagined. With open eyes I see the desk
before me; with eyes closed, I can imagine it. I lay my hand on it and
feel it; I can, without laying my hand on it, imagine that I feel it.
I raise my eyes, and see the pictures on the wall opposite me; I can
sit here and call before my mind the image of the door by which the
house is entered.
What is the difference between sense and imagination? It must be a
difference of which we are all somehow conscious, for we unhesitatingly
distinguish between the things we perceive and the things we merely
imagine.
It is well to remember at the outset that the two classes of
experiences are not wholly different. The blue color that I imagine
seems blue. It does not lose this quality because it is only
imaginary. The horse that I imagine seems to have four legs, like a
horse perceived. As I call it before my mind, it seems as large as the
real horse. Neither the color, nor the size, nor the distribution of
parts, nor any other attribute of the sort appears to be different in
the imaginary object from what it is in the object as given in
sensation.
The two experiences are, nevertheless, not the same; and every one
knows that they are not the same. One difference that roughly marks
out the two classes of experiences from one another is that, as a rule,
our sense-experiences are more vivid than are the images that exist in
the imagination.
I say, as a rule, for we cannot always remark this difference.
Sensations may be very clear and unmistakable, but they may also be
very faint and indefinite. When a man lays his hand firmly on my
shoulder, I may be in little doubt whether I feel a sensation or do
not; but when he touches my back very lightly, I may easily be in
doubt, and may ask myself in perplexity whether I have really been
touched or whether I have merely imagined it. As a vessel recedes and
becomes a mere speck upon the horizon, I may well wonder, before I feel
sure that it is really quite out of sight, whether I still see the dim
little point, or whether I merely imagine that I see it.
On the other hand, things merely imagined may sometimes be very vivid
and insistent. To some persons, what exists in the imagination is dim
and indefinite in the extreme. Others imagine things vividly, and can
describe what is present only to the imagination almost as though it
were something seen. Finally, we know that an image may become so
vivid and insistent as to be mistaken for an external thing. That is
to say, there are such things as hallucinations.
The criterion of vividness will not, therefore, always serve to
distinguish between what is given in the sense and what is only
imagined. And, indeed, it becomes evident, upon reflection, that we do
not actually make it our ultimate test. We may be quite willing to
admit that faint sensations may come to be confused with what is
imagined, with "ideas," but we always regard such a confusion as
somebody's error. We are not ready to admit that things perceived
faintly are things imagined, or that vivid "ideas" are things perceived
by sense.
Let us come back to the illustrations with which we started. How do I
know that I perceive the desk before me; and how do I know that,
sitting here, I imagine, and do not see, the front door of the house?
My criterion is this: when I have the experience I call "seeing my
desk," the bit of experience which presents itself as my desk is in a
certain setting. That is to say, the desk seen must be in a certain
relation to my body, and this body, as I know it, also consists of
experiences. Thus, if I am to know that I see the desk, I must realize
that my eyes are open, that the object is in front of me and not behind
me, etc.
The desk as seen varies with the relation to the body in certain ways
that we regard as natural and explicable. When I am near it, the
visual experience is not just what it is when I recede from it. But
how can I know that I am near the desk or far from it? What do these
expressions mean? Their full meaning will become clearer in the next
chapter, but here I may say that nearness and remoteness must be
measured for me in experiences of some sort, or I would never know
anything as near to or far from my body.
Thus, all our sensory experiences are experiences that fall into a
certain system or order. It is a system which we all recognize
implicitly, for we all reject as merely imaginary those experiences
which lack this setting. If my eyes are shut--I am speaking now of the
eyes as experienced, as felt or perceived, as given in sensation--I
never say; "I see my desk," no matter how vivid the image of the
object. Those who believe in "second sight" sometimes talk of seeing
things not in this setting, but the very name they give to the supposed
experience indicates that there is something abnormal about it. No one
thinks it remarkable that I see the desk before which I perceive myself
to be sitting with open eyes. Every one would think it strange if I
could see and describe the table in the next room, now shut away from
me. When a man thinks he hears his name pronounced, and, turning his
head, seeks in vain for the speaker, he sets his experience down as a
hallucination. He says, I did not really hear that; I merely imagined
it.
May one not, with open eyes, have a hallucination of vision, just as
one may seem to hear one's name pronounced when no one is by?
Certainly. But in each case the experience may be proved to be a
hallucination, nevertheless. It may be recognized that the sensory
setting is incomplete, though it may not, at first, seem so. Thus the
unreal object which seems to be seen may be found to be a thing that
cannot be touched. Or, when one has attained to a relatively complete
knowledge of the system of experiences recognized as sensory, one may
make use of roundabout methods of ascertaining that the experience in
question does not really have the right setting. Thus, the ghost which
is seen by the terrified peasant at midnight, but which cannot be
photographed, we may unhesitatingly set down as something imagined and
not really seen.
All our sensations are, therefore, experiences which take their place
in a certain setting. This is our ultimate criterion. We need not
take the word of the philosopher for it. We need only reflect, and ask
ourselves how we know that, in a given case, we are seeing or hearing
or touching something, and are not merely imagining it. In every case,
we shall find that we come back to the same test. In common life, we
apply the test instinctively, and with little realization of what we
are doing.
And if we turn to the psychologist, whose business it is to be more
exact and scientific, we find that he gives us only a refinement of
this same criterion. It is important to him to distinguish between
what is given in sensation and what is furnished by memory or
imagination, and he tells us that sensation is the result of a message
conducted along a sensory nerve to the brain.
Here we see emphasized the relation to the body which has been
mentioned above. If we ask the psychologist how he knows that the body
he is talking about is a real body, and not merely an imagined one, he
has to fall back upon the test which is common to us all. A real hand
is one which we see with the eyes open, and which we touch with the
other hand. If our experiences of our own body had not the setting
which marks all sensory experiences, we could never say: I _perceive_
that my body is near the desk. When we call our body real, as
contrasted with things imaginary, we recognize that this group of
experiences belongs to the class described; it is given in sensation,
and is not merely thought of.
It will be observed that, in distinguishing between sensations and
things imaginary, we never go beyond the circle of our experiences. We
do not reach out to a something _beyond_ or _behind_ experiences, and
say: When such a reality is present, we may affirm that we have a
sensation, and when it is not, we may call the experience imaginary.
If there were such a reality as this, it would do us little good, for
since it is not supposed to be perceived directly, we should have to
depend upon the sensations to prove the presence of the reality, and
could not turn to the reality and ask it whether we were or were not
experiencing a sensation. The distinction between sensations and what
is imaginary is an _observed_ distinction. It can be _proved_ that
some experiences are sensory and that some are not. This means that,
in drawing the distinction, we remain within the circle of our
experiences.
There has been much unnecessary mystification touching this supposed
reality behind experiences. In the next chapter we shall see in what
senses the word "reality" may properly be used, and in what sense it
may not. There is a danger in using it loosely and vaguely.
16. MAY WE CALL "THINGS" GROUPS OF SENSATIONS?--Now, the external world
seems to the plain man to be directly given in his sense experiences.
He is willing to admit that the table in the next room, of which he is
merely thinking, is known at one remove, so to speak. But this desk
here before him: is it not known directly? Not the mental image, the
mere representative, but the desk itself, a something that is physical
and not mental?
And the psychologist, whatever his theory of the relation between the
mind and the world, seems to support him, at least, in so far as to
maintain that in sensation the external world is known as directly as
it is possible for the external world to be known, and that one can get
no more of it than is presented in sensation. If a sense is lacking,
an aspect of the world as given is also lacking; if a sense is
defective, as in the color-blind, the defect is reflected in the world
upon which one gazes.
Such considerations, especially when taken together with what has been
said at the close of the last section about the futility of looking for
a reality behind our sensations, may easily suggest rather a startling
possibility. May it not be, if we really are shut up to the circle of
our experiences, that the physical things, which we have been
accustomed to look upon as non-mental, are nothing more than complexes
of sensations? Granted that there seems to be presented in our
experience a material world as well as a mind, may it not be that this
material world is a mental thing of a certain kind--a mental thing
contrasted with other mental things, such as imaginary things?
This question has always been answered in the affirmative by the
idealists, who claim that all existence must be regarded as psychical
existence. Their doctrine we shall consider later (sections 49 and
53). It will be noticed that we seem to be back again with Professor
Pearson in the last chapter.
To this question I make the following answer: In the first place, I
remark that even the plain man distinguishes somehow between his
sensations and external things. He thinks that he has reason to
believe that things do not cease to exist when he no longer has
sensations. Moreover, he believes that things do not always appear to
his senses as they really are. If we tell him that his sensations
_are_ the things, it shocks his common sense. He answers: Do you mean
to tell me that complexes of sensation can be on a shelf or in a
drawer? can be cut with a knife or broken with the hands? He feels
that there must be some real distinction between sensations and the
things without him.
Now, the notions of the plain man on such matters as these are not very
clear, and what he says about sensations and things is not always
edifying. But it is clear that he feels strongly that the man who
would identify them is obliterating a distinction to which his
experience testifies unequivocally. We must not hastily disregard his
protest. He is sometimes right in his feeling that things are not
identical, even when he cannot prove it.
In the second place, I remark that, in this instance, the plain man is
in the right, and can be shown to be in the right. "Things" are not
groups of sensations. The distinction between them will be explained
in the next section.
17. THE DISTINCTION BETWEEN SENSATIONS AND "THINGS"--Suppose that I
stand in my study and look at the fire in the grate. I am experiencing
sensations, and am not busied merely with an imaginary fire. But may
my whole experience of the fire be summed up as an experience of
sensations and their changes? Let us see.
If I shut my eyes, the fire disappears. Does any one suppose that the
fire has been annihilated? No. We say, I no longer see it, but
nothing has happened to the fire.
Again, I may keep my eyes open, and simply turn my head. The fire
disappears once more. Does any one suppose that my turning my head has
done anything to the fire? We say unhesitatingly, my sensations have
changed, but the fire has remained as it was.
Still, again, I may withdraw from the fire. Its heat seems to be
diminished. Has the fire really grown less hot? And if I could
withdraw to a sufficient distance, I know that the fire would appear to
me smaller and less bright. Could I get far enough away to make it
seem the faintest speck in the field of vision, would I be tempted to
claim that the fire shrunk and grew faint merely because I walked away
from it? Surely not.
Now, suppose that I stand on the same spot and look at the fire without
turning my head. The stick at which I am gazing catches the flame,
blazes up, turns red, and finally falls together, a little mass of gray
ashes. Shall I describe this by saying that my sensations have
changed, or may I say that the fire itself has changed? The plain man
and the philosopher alike use the latter expression in such a case as
this.
Let us take another illustration. I walk towards the distant house on
the plain before me. What I see as my goal seems to grow larger and
brighter. It does not occur to me to maintain that the house changes
as I advance. But, at a given instant, changes of a different sort
make their appearance. Smoke arises, and flames burst from the roof.
Now I have no hesitation in saying that changes are taking place in the
house. It would seem foolish to describe the occurrence as a mere
change in my sensations. Before it was my sensations that changed; now
it is the house itself.
We are drawing this distinction between changes in our sensations and
changes in things at every hour in the day. I cannot move without
making things appear and disappear. If I wag my head, the furniture
seems to dance, and I regard it as a mere seeming. I count on the
clock's going when I no longer look upon its face. It would be absurd
to hold that the distinction is a mere blunder, and has no foundation
in our experience. The rôle it plays is too important for that. If we
obliterate it, the real world of material things which seems to be
revealed in our experience melts into a chaos of fantastic experiences
whose appearances and disappearances seem to be subject to no law.
And it is worthy of remark that it is not merely in common life that
the distinction is drawn. Every man of science must give heed to it.
The psychologist does, it is true, pay much attention to sensations;
but even he distinguishes between the sensations which he is studying
and the material things to which he relates them, such as brains and
sense-organs. And those who cultivate the physical sciences strive,
when they give an account of things and their behavior, to lay before
us a history of changes analogous to the burning of the stick and of
the house, excluding mere changes in sensations.
There is no physicist or botanist or zoölogist who has not our common
experience that things as perceived by us--our experiences of
things--appear or disappear or change their character when we open or
shut our eyes or move about. But nothing of all this appears in their
books. What they are concerned with is things and their changes, and
they do not consider such matters as these as falling within their
province. If a botanist could not distinguish between the changes
which take place in a plant, and the changes which take place in his
sensations as he is occupied in studying the plant, but should tell us
that the plant grows smaller as one recedes from it, we should set him
down as weak-minded.
That the distinction is everywhere drawn, and that we must not
obliterate it, is very evident. But we are in the presence of what has
seemed to many men a grave difficulty. Are not things presented in our
experience only as we have sensations? what is it to perceive a thing?
is it not to have sensations? how, then, _can_ we distinguish between
sensations and things? We certainly do so all the time, in spite of
the protest of the philosopher; but many of us do so with a haunting
sense that our behavior can scarcely be justified by the reason.
Our difficulty, however, springs out of an error of our own. Grasping
imperfectly the full significance of the word "sensation," we extend
its use beyond what is legitimate, and we call by that name experiences
which are not sensations at all. Thus the external world comes to seem
to us to be not really a something contrasted with the mental, but a
part of the mental world. We accord to it the attributes of the
latter, and rob it of those distinguishing attributes which belong to
it by right. When we have done this, we may feel impelled to say, as
did Professor Pearson, that things are not really "outside" of us, as
they seem to be, but are merely "projected" outside--thought of as if
they were "outside." All this I must explain at length.
Let us come back to the first of the illustrations given above, the
case of the fire in my study. As I stand and look at it, what shall I
call the red glow which I observe? Shall I call it a _quality of a
thing_, or shall I call it a _sensation_?
To this I answer: _I may call it either the one or the other, according
to its setting among other experiences_.
We have seen (section 15) that sensations and things merely imaginary
are distinguished from one another by their setting. With open eyes we
see things; with our eyes closed we can imagine them: we see what is
before us; we imagine what lies behind our backs. If we confine our
attention to the bit of experience itself, we have no means of
determining whether it is sensory or imaginary. Only its setting can
decide that point. Here, we have come to another distinction of much
the same sort. That red glow, that bit of experience, taken by itself
and abstracted from all other experiences, cannot be called either a
sensation or the quality of a thing. Only its context can give us the
right to call it the one or the other.
This ought to become clear when we reflect upon the illustration of the
fire. We have seen that one whole series of changes has been
unhesitatingly described as a series of changes in my sensations. Why
was this? Because it was observed to depend upon changes in the
relations of my body, my senses (a certain group of experiences), to
the bit of experience I call the fire. Another series was described as
a series of changes in the fire. Why? Because, the relation to my
senses remaining unchanged, changes still took place, and had to be
accounted for in other ways.
It is a matter of common knowledge that they can be accounted for in
other ways. This is not a discovery of the philosopher. He can only
invite us to think over the matter and see what the unlearned and the
learned are doing at every moment. Sometimes they are noticing that
experiences change as they turn their heads or walk toward or away from
objects; sometimes they abstract from this, and consider the series of
changes that take place independently of this.
That bit of experience, that red glow, is not related only to my body.
Such experiences are related also to each other; they stand in a vast
independent system of relations, which, as we have seen, the man of
science can study without troubling himself to consider sensations at
all. This system is the external world--the external world as known or
as knowable, the only external world that it means anything for us to
talk about. As having its place in this system, a bit of experience is
not a sensation, but is a quality or aspect of a thing.
Sensations, then, to be sensations, must be bits of experience
considered in their relation to some organ of sense. They should never
be confused with qualities of things, which are experiences in a
different setting. It is as unpardonable to confound the two as it is
to confound sensations with things imaginary.
We may not, therefore, say that "things" are groups of sensations. We
may, if we please, describe them as complexes of qualities. And we may
not say that the "things" we perceive are really "inside" of us and are
merely "projected outside."
What can "inside" and "outside" mean? Only this. We recognize in our
experience two distinct orders, the _objective order_, the system of
phenomena which constitutes the material world, and the _subjective
order_, the order of things mental, to which belong sensations and
"ideas." That is "outside" which belongs to the objective order. The
word has no other meaning when used in this connection. That is
"inside" which belongs to the subjective order, and is contrasted with
the former.
If we deny that there is an objective order, an external world, and say
that everything is "inside," we lose our distinction, and even the word
"inside" becomes meaningless. It indicates no contrast. When men fall
into the error of talking in this way, what they do is to _keep_ the
external world and gain the distinction, and at the same time to _deny_
the existence of the world which has furnished it. In other words,
they put the clerk into a telephone exchange, and then tell us that the
exchange does not really exist. He is inside--of what? He is inside
of nothing. Then, can he really be inside?
We see, thus, that the plain man and the man of science are quite right
in accepting the external world. The objective order is known as
directly as is the subjective order. Both are orders of experiences;
they are open to observation, and we have, in general, little
difficulty in distinguishing between them, as the illustrations given
above amply prove.
18. THE EXISTENCE OF MATERIAL THINGS.--One difficulty seems to remain
and to call for a solution. We all believe that material things exist
when we no longer perceive them. We believe that they existed before
they came within the field of our observation.
In these positions the man of science supports us. The astronomer has
no hesitation in saying that the comet, which has sailed away through
space, exists, and will return. The geologist describes for us the
world as it was in past ages, when no eye was opened upon it.
But has it not been stated above that the material world is an order of
_experiences_? and can there be such a thing as an experience that is
not _experienced_ by somebody? In other words, can the world exist,
except as it is _perceived to exist_?
This seeming difficulty has occasioned much trouble to philosophers in
the past. Bishop Berkeley (1684-1753) said, "To exist is to be
perceived." There are those who agree with him at the present day.
Their difficulty would have disappeared had they examined with
sufficient care the meaning of the word "exist." We have no right to
pass over the actual uses of such words, and to give them a meaning of
our own. If one thing seems as certain as any other, it is that
material things exist when we do not perceive them. On what ground may
the philosopher combat the universal opinion, the dictum of common
sense and of science? When we look into his reasonings, we find that
he is influenced by the error discussed at length in the last
section--he has confused the phenomena of the two orders of experience.
I have said that, when we concern ourselves with the objective order,
we abstract or should abstract, from the relations which things bear to
our senses. We account for phenomena by referring to other phenomena
which we have reason to accept as their physical conditions or causes.
We do not consider that a physical cause is effective only while we
perceive it. When we come back to this notion of our perceiving a
thing or not perceiving it, we have left the objective order and passed
over to the subjective. We have left the consideration of "things" and
have turned to sensations.
There is no reason why we should do this. The physical order is an
independent order, as we have seen. The man of science, when he is
endeavoring to discover whether some thing or quality of a thing really
existed at some time in the past, is not in the least concerned to
establish the fact that some one saw it. No one ever saw the primitive
fire-mist from which, as we are told, the world came into being. But
the scientist cares little for that. He is concerned only to prove
that the phenomena he is investigating really have a place in the
objective order. If he decides that they have, he is satisfied; he has
proved something to exist. _To belong to the objective order is to
exist as a physical thing or quality_.
When the plain man and the man of science maintain that a physical
thing exists, they use the word in precisely the same sense. The
meaning they give to it is the proper meaning of the word. It is
justified by immemorial usage, and it marks a real distinction. Shall
we allow the philosopher to tell us that we must not use it in this
sense, but must say that only sensations and ideas exist? Surely not.
This would mean that we permit him to obliterate for us the distinction
between the external world and what is mental.
But is it right to use the word "experience" to indicate the phenomena
which have a place in the objective order? Can an experience be
anything but mental?
There can be no doubt that the suggestions of the word are
unfortunate--it has what we may call a subjective flavor. It suggests
that, after all, the things we perceive are sensations or percepts, and
must, to exist at all, exist in a mind. As we have seen, this is an
error, and an error which we all avoid in actual practice. We do not
take sensations for things, and we recognize clearly enough that it is
one thing for a material object to exist and another for it to be
perceived.
Why, then, use the word "experience"? Simply because we have no better
word. We must use it, and not be misled by the associations which
cling to it. The word has this great advantage: it brings out clearly
the fact that all our knowledge of the external world rests ultimately
upon those phenomena which, when we consider them in relation to our
senses, we recognize as sensations. We cannot start out from mere
imaginings to discover what the world was like in the ages past.
It is this truth that is recognized by the plain man, when he maintains
that, in the last resort, we can know things only in so far as we see,
touch, hear, taste, and smell them; and by the psychologist, when he
tells us that, in sensation, the external world is revealed as directly
as it is possible that it could be revealed. But it is a travesty on
this truth to say that we do not know things, but know only our
sensations of sight, touch, taste, hearing, and the like.[1]
[1] See the note on this chapter at the close of the volume.