I mentioned incidentally in the first section that it is conceivable
that failure to give adequate consideration to practical judgments may
have a compromising effect upon the consideration of other types. I
now intend to develop this remark with regard to sense perception as a
form of knowledge. The topic is so bound up with a multitude of
perplexing psychological and epistemological traditions that I have
first to make it reasonably clear what it is and what it is not which
I propose to discuss. I endeavored in an earlier series of papers[90]
to point out that the question of the _material_ of sense perception
is not, as such, a problem of the theory of knowledge at all, but
simply a problem of the occurrence of a certain material--a problem of
causal conditions and consequences. That is to say, the problem
presented by an image[91] of a bent stick, or by a dream, or by
"secondary" sensory qualities is properly a problem of physics--of
conditions of occurrence, and not of logic, of truth or falsity, fact
or fiction. That the existence of a red _quale_ is dependent upon
disturbances of a certain velocity of a medium in connection with
certain changes of the organism is not to be confused with the notion
that red is a way of knowing, in some more or less adequate fashion,
some more "real" object or else of knowing itself. The fact of
causation--or functional dependence--no more makes the _quale_ an
"appearance" to the mind of something more real than itself or of
itself than it makes bubbles on the water a real fish transferred by
some cognitive distortion into a region of appearance. With a little
stretching we may use the term appearance in either case, but the term
only means that the red _quale_ or the water-bubble is an _obvious_ or
conspicuous thing from which we infer something else not so obvious.
This position thus freely resumed here needs to be adequately guarded
on all sides. It implies that the question of the existence or
presence of the _subject-matter_ of even a complex sense perception
may be treated as a question of physics. It also implies that the
_existence_ of a sense perception may be treated as a problem of
physics. But the position is not that _all_ the problems of sense
perception are thereby exhausted. There is still, on the contrary, the
problem of the cognitive status of sense perception. So far from
denying this fact, I mean rather to emphasize it in holding that this
knowledge aspect is not to be identified--as it has been in both
realistic and idealistic epistemologies--with the simple _occurrence_
of presented subject-matter and with the _occurrence_ of a perceptive
act. It is often stated, for example, that primitive sense objects
when they are stripped of all inferential material cannot possibly be
false--but with the implication that they, therefore, must be true.
Well, I meant to go this statement one better--to state that they are
neither true nor false--that is, that the distinction of true-or-false
is as irrelevant and inapplicable as to any other existence, as it is,
say, to being more than five feet high or having a low blood pressure.
This position when taken leaves over the question of sense perception
as knowledge, as capable of truth or falsity. It is this question,
then, which I intend to discuss in this paper.
I
My first point is that some sense perceptions at least (as matter of
fact the great bulk of them), are without any doubt forms of practical
judgment--or, more accurately, are terms in practical judgments as
propositions of what to do. When in walking down a street I see a sign
on the lamp-post at the corner, I assuredly see a sign. Now in
ordinary context (I do not say always or necessarily) this is a sign
of what to do--to continue walking or to turn. The other term of the
proposition may not be stated or it may be; it is probably more often
tacit. Of course, I have taken the case of the sign purposely. But the
case may be extended. The lamp-post as perceived is to a lamp-lighter
a sign of something else than a turn, but still a sign of something to
be done. To another man, it may be a sign of a possible support. I am
anxious not to force the scope of cases of this class beyond what
would be accepted by an unbiased person, but I wish to point out that
certain features of the perceived object, as a cognitive term, which
do not seem at first sight to fall within this conception of the
object, as, an intellectual sign of what to do, turn out upon analysis
to be covered by it. It may be said, for example, that our supposed
pedestrian perceives much besides that which serves as evidence of the
thing to be done. He perceives the lamp-_post_, for example, and
possibly the carbons of the arc. And these assuredly do not enter into
the indication of what to do or how to do it.
The reply is threefold. In the first place, it is easy--and usual--to
read back into the sense perception more than was actually in it. It
is easy to _recall_ the familiar features of the lamp-post; it is
practically impossible--or at least very unusual--to recall what was
actually perceived. So we read the former into the latter. The
_tendency_ is for actual perception to limit itself to the minimum
which will serve as sign. But, in the second place, since it is never
wholly so limited, since there is always a surplusage of perceived
object, the fact stated in the objection is admitted. But it is
precisely this surplusage which has not _cognitive_ status. It does
not serve as a sign, but neither is it _known_, or a term in
knowledge. A child, walking by his father's side, with no aim and
hence no reason for securing indications of what to do, will probably
see more in his idle curiosity than his parent. He will have more
presented material. But this does not mean that he is making more
propositions, but only that he is getting more material for possible
propositions. It means, in short, that he is in an aesthetic attitude
of realization rather than in a cognitive attitude. But even the most
economical observer has some aesthetic, non-cognitive surplusage.[92]
In the third place, surplusage is necessary for the operation of the
signifying function. Independently of the fact that surplusage may be
required to render the sign specific, action is free (its variation is
under control) in the degree in which _alternatives_ are present. The
pedestrian has probably the two alternatives in mind: to go straight
on or to turn. The perceived object might indicate to him another
alternative--to stop and inquire of a passer-by. And, as is obvious in
a more complicated case, it is the extent of the perceived object
which both multiplies alternative ways of acting and gives the grounds
for selecting among them. A physician, for example, deliberately
avoids such hard-and-fast alternatives as have been postulated in our
instance. He does not observe simply to get an indication of whether
the man is well or ill; but in order to determine what to do he
extends his explorations over a wide field. Much of his perceived
object field is immaterial to what he finally does; that is, does not
serve as sign. But it is all relevant to _judging_ what he is to do.
Sense perception as a term in practical judgment _must_ include more
than the element which finally serves as sign. If it did not, there
would be no perception, but only a direct stimulus to action.[93]
The conclusion that such perceptions as we have been considering are
terms in an inference is to be carefully discriminated from the loose
statement that sense perceptions are unconscious inferences. There is
a great difference between saying that the perception of a shape
affords an indication for an inference and saying that the perception
of shape is itself an inference. That definite shapes would not be
perceived, were it not for neural changes brought about in prior
inferences, is a possibility; it may be, for aught I know, an
ascertained fact. Such telescoping of a perceived object with the
object inferred from it may be a constant function; but in any case
the telescoping is not a matter of a present inference going on
unconsciously, but is the result of an organic modification which has
occurred in consequence of prior inferences. In similar fashion, to
say that to see a table is to get an indication of something to write
on is in no way to say that the perception of a table is an inference
from sensory data. To say that certain earlier perceived objects not
having as perceived the character of a table have now "fused" with the
results of inferences drawn from them is not to say that the
perception of the table is now an inference. Suppose we say that the
first perception was of colored patches; that we inferred from this
the possibility of reaching and touching, and that on performing these
acts we secured certain qualities of hardness, smoothness, etc., and
that these are now all fused with the color-patches. At most this only
signifies that certain _previously_ inferred qualities have now become
consolidated with qualities from which they were formerly inferred.
And such fusion or consolidation is precisely _not inference_. As
matter of fact, such "fusion" of qualities, given and _formerly_
inferred, is but a matter of speaking. What has really happened is
that _brain_ processes which formerly happened successively now happen
simultaneously. What we are dealing with is not a fact of cognition,
but a fact of the organic conditions of the occurrence of an act of
perception.
Let us apply the results to the question of sense "illusions." The
bent reed in the water comes naturally to mind. Purely physical
considerations account for the refraction of the light which produces
an optical image of a bent stick. This has nothing to do with
knowledge or with sense perception--with seeing. It is simply and
wholly a matter of the properties of light and a lens. Such
refractions are constantly produced without our noting them. In the
past, however, light refracted and unrefracted has been a constant
stimulus to responsive actions. It is a matter of the native
constitution of the organism that light stimulates the eyes to follow
and the arms to reach and the hands to clutch and handle. As a
consequence, certain arrangements of reflected and refracted light
have become a sign to perform certain specific acts of handling and
touching. As a rule, stimuli and reactions occur in an approximately
homogeneous medium--the air. The system of signs or indexes of action
set up has been based upon this fact and accommodated to it. A habit
or bias in favor of a certain kind of inference has been set up. We
infer from a bent ray of light that the hand, in touching the
reflecting object, will, at a certain point, have to change its
direction. This habit is carried over to a medium in which the
conclusion does not hold. Instead of saying that light is bent--which
it is--we _infer_ that the stick is bent: we infer that the hand could
not protract a straight course in handling the object. But an expert
fisherman never makes such an error in spearing fish. Reacting in
media of different refractive capacities, he bases his signs and
inferences upon the conditions and results of his media. I see no
difference between these cases and that of a man who can read his own
tongue. He sees the word "pain" and infers it means a certain physical
discomfort. As matter of fact, the thing perceived exists in an
unfamiliar medium and signifies bread. To the one accustomed to the
French language the right inference occurs.[94] There is neither error
nor truth in the optical image: It just exists physically. But we take
it for something else, we behave to it as if it were something else.
We _mis_-take it.