We are brought to a consideration of the notion of "primitive" sense
data. It was long customary to treat the attempt to define true
knowledge in terms derived from sense data as a confusion of
psychology--or the history of the growth of knowledge--with logic, the
theory of the character of knowledge as knowledge. As matter of fact,
there _is_ confusion, but in the opposite direction. The attempt
involved a confusion of logic with psychology--that is, it treated a
phase of the technique of inference as if it were a natural history of
the growth of ideas and beliefs.
The chief source of error in ordinary inference is an unrecognized
complexity of data. Perception which is not experimentally controlled
fails to present sufficiently wide data to secure differentia of
possible inferences, and it fails to present, even in what is given,
lines of cleavage which are important for proper inference. This is
only an elaborate way of saying what scientific inquiry has made
clear, that, for purposes of inference as to conditions of production
of what is present, _ordinary_ sense perception is too narrow, too
confused, too vivid as to some _quales_ and too blurred as to some
others. Let us confine our attention for the moment to confusion. It
has often been pointed out that sense qualities being just what they
are, it is illegitimate to introduce such notions as obscurity or
confusion into them: a slightly illuminated color is just as
irretrievably what it is, as clearly itself, as an object in the broad
glare of noonday. But the case stands otherwise when the _quale_ is
taken as a datum for inference. It is not so easy to identify a
perceived object _for purposes of inference_ in the dusk as in bright
light. From the standpoint of an inference to be effected, the
confusion is the same as an unjustifiable simplification. This
over-simplification has the effect of making the _quale_, as a term of
inference, ambiguous. To infer from it is to subject ourselves to the
danger of all fallacies of ambiguity which are expounded in the
textbooks. The remedy is clearly the resolution, by experimental
means, of what seems to be a simple datum into its "elements." This is
a case of analysis; it differs from other modes of analysis only in
the subject-matter upon which it is directed, viz., something which
had been previously accepted as a simple whole. The result of this
analysis is the existence as objects of perception of isolated
qualities like the colors of the spectrum scientifically determined,
the tones of the scale in all their varying intensities, etc., in
short, the "sensations" or sense qualities of contemporary psychology
textbooks or the "simple ideas" of sensation of Locke or the "objects
of sense" of Russell. They are the material of sense perception
discriminated for the purpose of better inferences.
Note that these simple data or elements are not original,
psychologically or historically; they are _logical_ primitives--that
is, irreducible for purposes of inference. They are simply the most
unambiguous and best defined objects of perception which can be
secured to serve as _signs_. They are experimentally determined, with
great art, precisely because the naturally given, the customary,
objects in perception have been ambiguous or confused terms in
inference. Hence they are replaced, through experimental means
involving the use of wide scientific knowledge deductively employed,
by simpler sense objects. Stated in current phraseology, "sensations"
(i.e., qualities present to sense) are not the elements out of which
perceptions are composed, constituted, or constructed; they are the
finest, most carefully discriminated objects of perception. We do not
first perceive a single, thoroughly defined shade, a tint and hue of
red; its perception is the last refinement of observation. Such things
are the limits of perception, but they are final, not initial, limits.
They are what is perceived to be given under the most favorable
possible conditions; conditions, moreover, which do not present
themselves accidentally, but which have to be intentionally and
experimentally established, and detection of which exacts the use of a
vast body of scientific propositions.
I hope it is now evident what was meant by saying that current logic
presents us not with a confusion of psychology with logic, but with a
wholesale mistaking of logical determinations for facts of
psychology. The confusion was begun by Locke--or rather made
completely current through the enormous influence exercised by
Locke--and some reference to Locke may be of aid in clearing up the
point. Locke's conception of knowledge was logical, not psychological.
He meant by knowledge thoroughly justified beliefs or propositions,
"certainty," and carefully distinguished it from what passed current
as knowledge at a given time. The latter he called "assent," opinion,
belief, or judgment. Moreover, his interest in the latter was logical.
He was after an art of controlling the proper degree of assent to be
given in matters of probability. In short, his sole aim was to
determine certainty where certainty is possible and to determine the
due degree of probability in the much vaster range of cases where only
probability is attainable. A natural history of the growth of
"knowledge" in the sense of what happens to pass for knowledge was the
last of his interests. But he was completely under the domination of
the ruling idea of his time; namely, that _Nature_ is the norm of
truth. Now the earliest period of human life presents the "work of
nature" in its pure and unadulterated form. The normal is the
original, and the original is the normative. Nature is both beneficent
and truthful in its work; it retains all the properties of the Supreme
Being whose vice-regent it is. To get the logical ultimates we have
only, therefore, to get back to the natural primitives. Under the
influence of such deistic ideas, Locke writes a mythology of the
history of knowledge, starting from clear and distinct meanings, each
simple, well defined, sharply and unambiguously just what it is on its
face, without concealments and complications, and proceeds by
"natural" compoundings up to the store of complex ideas, and to the
perception of simple relations of agreement among ideas: a perception
always certain if the ideas are simple, and always controllable in the
case of complex ideas if we consider the simple ideas and their
compoundings. Thus he established the habit of taking logical
discriminations as historical or psychological primitives--as
"sources" of beliefs and knowledge instead of as checks upon inference
and as means of knowing.
I hope reference to Locke will not make a scapegoat. I should not have
mentioned him if it were not that this way of looking at things found
its way over into orthodox psychology and then back again into the
foundations of logical theory. It may be said to be the stock in trade
of the school of empiricist logicians, and (what is even more
important) of the other schools of logic whenever they are dealing
with propositions of perception and observation: _vide_ Russell's
trusting confidence in "atomic" propositions as psychological
primitives. It led to the supposition that there is a kind of
_knowledge_ or simple apprehension (or sense acquaintance) implying no
inference and yet basic to inference. Note, if you please, the
multitude of problems generated by thinking of whatever is present in
experience (as sensory qualities are present) as if it were
intrinsically and apart from the use made of its subject-matter of
knowledge.
_a_) The mind-body problem becomes an integral part of the problem of
knowledge. Sense organs, neurones, and neuronic connections are
certainly involved in the occurrence of a sense quality. If the
occurrence of the latter is in and of itself a mode of knowledge, it
becomes a matter of utmost importance to determine just how the sense
organs take part in it. If one is an idealist he responds with joy to
any intimation that the "process of apprehension" (that is, speaking
truly, the physical conditions of the occurrence of the sensory datum)
transforms the extra-organic stimulus: the alteration is testimony
somehow to the constitutive nature of mind! But if he is a realist he
conceives himself under obligation to show that the external stimulus
is transmitted without any alteration and is apprehended just as it
is; color must be shown to be simply, after all, a compacting of
vibrations--or else the validity of knowledge is impugned! Recognize
that knowledge is something _about_ the color, whether about its
conditions or causes or consequences or whatever, and that we don't
have to identify color itself with a mode of knowing, and the
situation changes. We know a color when we understand, just as we know
a thunder-storm when we understand. More generally speaking, the
relation of brain-change to consciousness is thought to be an
essential part of the problem of knowledge. But if the brain is
involved in knowing simply as part of the mechanism of acting, as the
mechanism for co-ordinating partial and competing stimuli into a
single scheme of response, as part of the mechanism of actual
experimental inquiry, there is no miracle about the participation of
the brain in knowing. One might as well make a problem of the fact
that it takes a hammer to drive a nail and takes a hand to hold the
hammer as to make a problem out of the fact that it also requires a
physical structure to discover and to adapt the particular acts of
holding and striking which are needed.
_b_) The propositions of physical science are not found among the data
of apprehension. Mathematical propositions may be disposed of by
making them purely a priori; propositions about sense objects by
making them purely a posteriori.[95] But physical propositions, such
as make up physics, chemistry, biology, to say nothing of propositions
of history, anthropology, and society, are neither one nor the other.
I cannot state the case better than Mr. Russell has stated it,
although, I am bound to add, the stating did not arouse in Mr. Russell
any suspicion of the premises with which he was operating. "Men of
science, for the most part, are willing to condemn immediate data as
'merely subjective,' while yet maintaining the truth of the physics
inferred from those data. But such an attitude, though it may be
_capable_ of justification, obviously stands in need of it; and the
only justification possible must be one which exhibits matter as a
logical construction from sense data.... It is therefore necessary to
find some way of bridging the gulf between the world of physics and
the world of sense."[96] I do not see how anyone familiar with the
two-world schemes which have played such a part in the history of
humanity can read this statement without depression. And if it
occurred to one that the sole generating condition of _these_ two
worlds is the assumption that sense objects are modes of apprehension
or knowledge (are so intrinsically and not in the use made of them),
he might think it a small price to pay to inquire into the standing of
this assumption. For it was precisely the fact that sense perception
and physical science appeared historically (in the seventeenth
century) as rival modes of knowing the same world which led to the
conception of sense objects as "subjective"--since they were so
different from the objects of science. Unless sense and science had
both first been thought of as modes of knowing and then as modes of
knowing the same things, there would not have been the slightest
reason for regarding immediate data, as "merely subjective." They
would have been natural phenomena, like any other. That they are
phenomena which involve the interaction of an organism with other
things is just an important discovery about them, as is also a
discovery about starch in plants.
Physical science is the _knowledge_ of the world by their means. It is
a rival, not of them, but of the medley of prior dogmas,
superstitions, and chance opinions about the world--a medley which
grew up and nourished precisely because of absence of a will to
explore and of a technique for detecting unambiguous data. That Mr.
Russell, who is a professed realist, can do no better with the problem
(once committed to the notion that sense objects are of themselves
_objects_ of knowledge) than to hold that although the world of
physics is not a legitimate inference from sense data, it is a
permissible logical construction from them--permissible in that it
involves no logical inconsistencies--suggests that the pragmatic
difference between idealist and realist--of this type--is not very
great. From necessary ideal constructions to permissible logical
constructions involves considerable difference in technique but no
perceptible practical difference. And the point of this family
likeness is that both views spring from regarding sense perception and
science as ways of knowing the same objects, and hence as rivals until
some scheme of conciliation has been devised.
_c_) It is but a variant of this problem to pass to what may be called
either the ego-centric predicament or the private-public problem.
Sense data differ from individual to individual. If they are
recognized to be natural events, this variation is no more significant
than any change depending upon variation of generating conditions. One
does not expect two lumps of wax at different distances from a hot
body to be affected exactly alike; the upsetting thing would be if
they were. Neither does one expect cast-iron to react exactly as does
steel. That organisms, because of different positions or different
internal structures, should introduce differences in the phenomena
which they respectively have a share in producing is a fact of the
same nature. But make the sense qualities thus produced not natural
events (which may then be made either objects of inquiry or means of
inquiry into something else) but modes of knowing, and every such
deviation marks a departure from true knowing: it constitutes an
anomaly. Taken _en masse_ the deviations are so marked as to lead to
the conclusion (even on the part of a realist like Mr. Russell) that
they constitute a world of private existences, which, however, may be
correlated without logical inconsistency with other such worlds. Not
all realists are Leibnizian monadists as is Mr. Russell; I do not wish
to leave the impression that all come to just this solution. But all
who regard sense data as apprehensions have on their hands in some
form the problem of the seemingly distorting action exercised by the
individual knower upon a public or common thing known or believed in.