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C.A. Strong

The crucial question, in the problem of sense-perception, is as to the nature of the datum. By “datum” I mean what we are immediately conscious of. Six different views as to this have succeeded each other in the course of modern philosophy: (1) That the datum is the real thing; (2) that it is an ideal representative of the real thing ; (3) that it is an ideal thing, psychological in its nature; (4) that it is an ideal thing, logical in its nature; (5) that it is a thing of psychological nature, but real; (6) that it is a thing of logical nature, but real — naïve realism, representationism, psychological subjectivism, logical subjectivism, psychological objectivism, logical objectivism. The view I shall try to recommend in this article, distinct from any of these, is (7) that the datum is the logical essence of the real thing. By “essence” I mean its what divorced from its that — its entire concrete nature, including its sensible character, but not its existence. To establish this, it will be necessary to show (1) that the things we are conscious of in sense-perception, as distinguished from the things we believe or affirm, are not the actual external existences; (2) that, on the other hand, they are not internal or psychical existences, either representative of the external ones or non-representative; (3) that, while they are logical entities — entities of the logical type they are not identifiable with the things we perceive, but are only the detached concrete natures or “essences” of those things.1 Thus the three divisions of our discussion are marked out for us.


That they are the real things is of course the conviction of common sense. Common sense will not admit that objects are not really coloured, and sonorous, and hot and cold; and the leading motive of some recent philosophers seems to be a desire to justify common sense in this point. This can be done only by contradicting common sense on a much weightier point, namely, by asserting that objects are capable of possess ing at the same moment and in the same spot contradictory qualities. For it is undeniable that an object which one person perceives as red another perceives as green, or as so like green as to be indistinguishable from it, and that where most people perceive a variety of colours some persons see only a more or less uniform grey. It is undeniable that a straight stick thrust in water looks bent, quite apart from any process of interpretation asserting that it actually is bent, and that the datum in this case (however much its character may be explicable by the operation of physical laws) consequently contradicts the object. It is undeniable that insane people hear sounds where there is no external sound, or none such as they hear. These are all cases of perceptual (as distinguished from intellective) error, and it is evident that they can be harmonized with the view that the data are the real things only by partially contradicting this view and asserting that whenever we are perceptually wrong they are not the real things, or else by entertaining the far from common-sense theory that because a thing is red that is no reason why it should not be also green (in the same place and at the same moment), and that because a thing is white that is no reason why it should not be also black.
      It is worth noting why perceptual error is possible. It is possible because data are directly dependent on the individual organism, not on the external object, varying in their character with the constitution of the sense-organs and the way in which these are affected, and only secondarily and indirectly with the external thing. Thus the insane person hears hallucinatory sounds because his auditory brain-centre is abnormally irritated; the colour-blind person sees red as green because his retina or his visual brain-centre is not normally constituted; the straight stick appears bent because the light-rays have been accidentally refracted at the surface of the water, etc. We have no power of penetrating to the object itself and intuiting it immediately, but are dependent for our information concerning it on the effects which it is able to produce within the body. In a word, data are subject to the law of psychophysical correlation.
      There is, then, a fundamental opposition between data and physical things, as science conceives these physical things conceived as in a continuous time and space and as possessing no characters that contradict each other. An opposition such that, if we say that data are real, we are forced to say that physical things are not real — that they are arbitrary selections from data, or intellectual constructions made on the basis of data; while, if we say that physical things are real — as I think we must — we are forced to conclude that data, as such, are not real. Either heat and cold just as we feel them are real, and then those vibrations of molecules which physicists assign as their objective cause are not real — except as other data of touch or as data of sight; or else the molecular vibrations are real, and then the data are not so. Either colour is real, and then the oscillations of the luminiferous ether, reflected from the surfaces of objects, by which science explains it, are not real — and what we are told about the velocity of light, and its source in the sun and the stars, and the activity of atoms as its cause, is only so much intellectual deduction from and gloss upon the phenomena of colour and luminosity; or, if the physical facts, just as science describes them, are real, then the data are not so. Reality is something attributed to the data, solely in the sense that there are objects of which they are data; and when we learn that other somewhat different data — namely, those asserted by science — would more accurately present these objects, all excuse disappears for holding that the data themselves are real, i.e. continuously existent.
      How impossible it is to identify physical things with data simply as such, appears with especial clearness when we consider the spatial and temporal characters of data and of physical things respectively. As regards space, a consequence of the dependence of data on the organism is that, as objects move farther and farther away from us, the data presenting them become smaller. Thus a human being becomes half and then quarter his normal size, and finally a mere speck on the horizon. We cannot suppose, consistently with physics or even with everyday sense, that the size of his body actually changes. Here is, then, a series of changes and differences in data corresponding to no real changes or differences in objects — a proof positive that the two cannot be identical. Data are presentments of objects from the point of view of the organism, they are not objects themselves.
      Out of this principle of the diminution of apparent size with distance arises the whole element of perspective in visual perception. Some parts of a solid object are necessarily farther away from the eye than others, with the result of appearing proportionately smaller; in other words, the object is seen in perspective. Perspective represents a distortion of real things, which fails to strike us as in glaring contrast with their proper constitution only because we are so familiar with it. It has also its practical value: if the relative distance of different things from us did not appear on their face, we could not make that distinction between what is at hand and what is farther away which is so essential to practice. It is none the less evident that the world as sense-perception presents it and the world as it is by no means coincide. When we pass to time, this disparity becomes, if possible, even more evident. The distance of objects from us involves a difference in the time it takes them to produce impressions on us; a nearer object is perceived sooner than a farther one, but when the medium of action on us is light, the difference is so slight as to have no practical significance. It is only in the case of the stars that we perceive simultaneously events that are really years and even centuries apart. Yet, theoretically, and on a vastly minuter scale, the falling flakes of a snowstorm or the apparently simultaneous sounds of a battle field are equally non-coincident temporally. When we see a gun fired at some distance, and hear the report several seconds after seeing the flash, the temporal displacement of the datum with reference to the real event is brought sensibly home to us.
      All these (or the like) are well-worn examples in present-day controversy. It will be time to cease insisting on them when all parties recognize their inevitable consequence, that the physical thing cannot be identified with the datum as such. If, in the present section, we have now succeeded in proving this, the following among the views mentioned at the beginning of this paper will thereby have been excluded and disproved: ( 1 ) that the datum is the real thing — naïve realism; ( 3 ) and ( 4 ) psychological and logical subjectivism, ( 5 ) and ( 6 ) psychological and logical objectivism, in so far as they assert that the physical thing is identical with the datum. Consistently with the above considerations, the physical thing can only be either an intellectual construction made on the basis of data, or a real existence brought before us by data. Which of these it is will depend very largely on the nature of data. Once these are recognized not to be physical things, the most natural supposition, or at least the one that historically has proved the most tempting, is that they are psychological in their nature, that they are perceptions — of things, or perhaps sensations.


A psychical fact is commonly conceived to be a vision that flashes before the mind, the seeing and the thing seen being fused together into the unity of a single entity. In this way an emotion, as of anger; a sensation, as of pain or cold; a mental image, as of some one’s face, is supposed to exist. But the trouble is that, when we see faces, we do not see our seeing of them — we see only the faces; and the question therefore arises whether the consciousness is really given in and with the face, or the anger, or the pain, as this conception supposes it to be. James, after fruitless attempts to assure himself that he introspected it, bravely declared that it is not. What we take for consciousness, that thin, ethereal seeing of internal things, is, in his view, the sensations of attending, etc.
      In short, when we speak of anything as a “datum,” that which makes it a datum, the givenness, is not given along with the thing. It is an “external denomination,” it consists in a relation between the thing given and something else. What this something else is, is perfectly clear, verbally at least; it is “I,” myself — anything given is given to me. And the relation of being given, the givenness or awareness (these are names for the same thing viewed from opposite ends), is not given along with the things.
      Datum is therefore a treacherous word to use for what is given, since it suggests that the givenness is given along with the thing. Here lies the immense advantage of the term “essence.” For the first time we get the datum characterized with absolute logical sharpness. But the assumption that the givenness is given is the whole basis of the claim that the datum as such is psychological in its nature. Hence, with the replacing of the term “datum” by that of “essence,” the thing designated is recognized not to be psychological, and, since we have shown it not to be physical, the chances are that it is logical, an entity of the peculiar type belonging to logic.
      It will perhaps be argued that a pain or an anger does not cease to be psychological because we recognize that, when we introspect it, we perceive no awareness. In other words, what we see, apart from the seeing (introspecting), is in itself psychological. The reply is that, while this is true in the case of the pain and the anger, it is not true in the case of the face; what is given there is a physical thing (I mean the essence of a physical thing, not its existence). Still more obviously is this true when we do not merely imagine, but actually see, faces; if we abstract from the seeing or givenness, the entire datum is physical (in the sense of essence, not of existence); or, to put it in the usual way, it is “objective.” Nothing can be more justified than the insistence of neo-realists, and indeed of all sound epistemologists, that the original datum of sense-perception has nothing subjective about it in the psychological sense — largely as we have shown it to be often (if not always!) subjective in the logical sense. The psychical character of some data, then, does not lie in the fact that they are data, but in the accidental fact that a psychical thing, and not a physical thing, is given. Data as such, accordingly, are even in the case of psychological perception or introspection not psychological in their nature. And, once more, since they are also not physical (but at most presentments of the physical), the probability is that they are entities of logic.


Before exploring this hypothesis further, let us look for a moment at the characteristic terms and propositions in which the psychological account of the datum has usually been formulated. Objects have been defined as “perceptions,” their esse has been set down as percipi. Now a “perception” or, better, a “percept” means, in full, something perceived by me; hence to assert that the esse of a thing is percipi, if we take the assertion quite literally, is to say that it consists in a relation between it and something else. This is obviously absurd. It is only if you conceive consciousness as a dimension of things, or things as made of consciousness, that the strict identification of esse and percipi becomes possible. But this is notoriously the current conception of consciousness; when we are told that “the perception is in the object” or that the fundamental data are “experienced-things,” it is evident that the conceptions of experience or perception involved contain no essential reference to an organism or ego. Whether this defect does not constitute a damning criticism of the subjectivist and objectivist theories in question, the judicious psychologist may be left to judge. The proposition that the esse of objects is percipi may, however, have a different sense; it may mean merely that objects continue to exist only so long as they are perceived. This, on the whole, I think, is the main intent of Berkeley. What is to be said of the proposition understood in this sense? In the first place, since the thing perceived is the physical thing, and since this is not identical with the datum, it does not follow in the least from the fact that, when perception ceases, there is no longer a datum or anything given, that the physical thing whose essence was given no longer exists. The utmost that could be thought to follow is that the datum no longer exists. But the datum, i.e. the essence given, no longer exists only in case it did exist when it was given — in case its givenness made it temporarily to exist. Givenness, however, as we have seen, is an external relation to an ego, and it is not obvious how the addition of this relation — how our awareness, in other words, of the essence can raise it from a state of non-existence to one of existence. On the contrary, the very nature of awareness seems to imply that what we are aware of remains the same, either as existent or as non-existent, whether we are aware of it or not, and that what is changed is only ourselves, by our enjoyment or awareness of it. Nevertheless it might perhaps be maintained that what in the intervals of our non-awareness has no existence, but is only a possibility of thought or perception, does by virtue of its given ness to us acquire a temporary kind of existence. And, in favour of this view, two principal arguments might be urged: ( 1 ) that through its givenness an essence acquires a definite position in time and space; ( 2 ) that the sensible vividness with which the perceptual essence is given proves it an existence. Before examining the value of these arguments, let us represent to ourselves a little more definitely the alternative possibility — that the datum is not an existence. There can be no question that we are capable of having things given to us which are not existences — e.g. centaurs, perfect squares, ideas of virtue. To deny the possibility that the mind can fix itself on what is not an existence and occupy itself for the moment solely with that , would involve the most extravagant consequences, and contradict the commonest facts. These non-existents are of course in the broadest sense universals. Yet they vary greatly in their degree of concreteness; centaur is more concrete than a perfect square, a perfect square is more concrete than virtue. The question will be whether a datum can be so concrete as even to have sensible vividness, and yet not be an existence, but only an entirely concrete universal, a universal of the lowest order. This would mean that the same datum exactly might be given to another person, or to the same person at a different time and place; in such wise that the datum as such would not be in time and space. That the data of perception are in fact universals of this description is the thesis of this paper, and is what has been meant by calling them essences. This view, and this view alone, seems to me to permit a satisfactory solution of all the difficulties connected with sense-perception.
      Now let us consider first the objection that the data of sense-perception are existences because they are in time and space. That a visual datum has a certain internal extension — being the vision of a large or a small object, a near or a distant one — is undeniable, and likewise that, if my body as well is given, I may be justified in affirming that the object, as close to my body, is “here.” But unless both the object and my body are real, and not dreams or hallucinations, the affirmation would not be valid; and this is something that can only be believed. In other words, the affirmation of locality has reference only to the physical things that the visual data bring before us, not to the visual data as such; the visual data as such are neither here nor there. They have no spatial relations to other possible visual data, but only spatial relations among their own parts — none, in short, that are not at this moment given. The fact that an essence is given, then, does not give it a position in space.
      Nor does it give it a position in time. Perceptual data doubtless have a certain internal duration, but their relation as wholes to other data, or to existences that are not data, is no part of them, and can consequently only be matter of affirmation. And the affirmation, as in the case of space, is really with reference to the temporal position of the physical thing given, not to that of the datum as such. The datum as such has no temporal position except that which lies in the fact of its givenness, and the temporal position is that of the givenness (or, more strictly, of the state of the ego to which it is given), not that of the essence.
      That the givenness of anything does not turn it into an existence belonging to the moment when it is given, may be shown by two arguments. If it did, then I could not think of the past without turning it into a present fact; in short, I could not think of the past at all. Existences, again, are always particular facts; and if thinking of anything turned it into a present existence, then in thinking of man in general or of virtue I should turn them into particular present existences; in other words, I could not think of them at all. That a particular present existence is involved in thinking of a universal or in thinking of the past I do not mean to deny; this is the psychic state which is the vehicle of the thought (about which more later); but at present we are concerned solely with what is thought of, the datum or essence.
      This may suffice to dispose of the argument that present data are necessarily in time and space; now for the argument that they are existences because they are sensibly vivid. This phrase marks the difference between imagining a thing and actually perceiving it; and there is undoubtedly a strong temptation to suppose that, when a thing is actually perceived, even the datum must be real. Our very idea of the unreal is the imaginary; while of the actually perceived we say, “Seeing is believing.” But note that this very maxim confesses that the real is not seen to be such, but believed upon the evidence of sight. In other words, it is hard for the hallucinated person to believe that he is so, the dreamer scarcely knows that he dreams. The datum in dreaming and hallucination is only a candidate for affirmation, a means of affirming the reality of the physical thing — it is not itself real.
      The main source of our tendency to think the datum an existence on the ground of its sensible vividness is, I think, our confusing it with the psychic state which is its vehicle. As we should not perceive if we had not sense-organs, so no data would be given if these and the connected brain were not endowed with sensibility. There are states of our sensibility which do not bring before us objects other than themselves—e.g. anger, or pain, or, in some cases, chill. An emotion of anger is not a perception of a state of our body; it is a floating psychical condition , representing to be sure our reaction to an object. A pain, such as toothache, is apt to be localised in a definite spot, and, in so far, serves to bring before us the morbid process occurring at that spot; but this element of locality and physical reference is extraneous to the pain itself, and we can, if we wish, attend solely to the latter, in which case what we have before us is a pure state of our sensibility. Similarly with cold: it may bring before us a cold object, or it may be taken in itself as a state of our sensibility.
      Now states of our sensibility do not cease to be such when they are used to bring before us objects. When I touch ice, I still feel, and feel in the particular way called feeling cold; when I hear an external sound, I still hear; and when I see, I do so by means of states of my sensibility which I know not how to describe except as visual sensations. At any moment I can turn my attention, at will, from the seen, heard, or felt object to the visual, auditory, or tactile sensation, the mere state of my sensibility; and, if my hypothesis is correct, this last is not brought into existence by the fact of my attending to it, but is simply brought under view. This state of my sensibility is indeed an existence, though a transitory one; if it did not exist, it would be impossible for the external object, the ice, or the bell, or the spray of leaves, to appear before us as a datum. But because the vehicle of the givenness of this essence is an existence, it does not follow that the essence itself is one. If it were, we should have three existences concerned in sense-perception — the physical thing, the state of our sensibility, and the essence — which even the most determined multipliers of metaphysical entities will think too many.
      The example that seems to me to bring out most clearly the difference between the perceptual essence and the sensation is that given by James, of the after-image of the sun projected successively on the thumb-nail, on the wall of the room, and on a mountain-side, and bringing before us thus three (false) external objects of very different size. Throughout this experience I seem to myself to be able to observe that the after-image retains the same sensible size. If so, the variation in the size of the objects — which is an essential part of what is given (when we do not introspect the sensation but perceive the false objects ) — must be something which the after-image has as a symbol and not as a sensible fact. What is given to us, in other words, in sense-perception is the sensation as a meaning and not the sensation as a factor, to speak more correctly, what is given is the meaning and not the sensation. It is just as in reading, where what is present to the mind is the significance and not the mere printed characters. Now that this significance, or meaning, or essence, is not an existence and not in time and space, but, like the meaning when we think of a universal, a purely logical entity, is quite credible.
      Two objections may be made to my treatment of this example. First, it may be said that I am venturing unjustifiably beyond experience in suggesting that the after-image exists and retains its size when my attention is turned, not to it, but to the false objects. The sensation-granting that we can attend to a pure sensation exists only when we experience it; a sensation which no one has is absurd. And since the sensation cannot exist when we are attending to the objects, it cannot have a size. I admit that an unfelt sensation, in the sense in which the word sensation is ordinarily used, is absurd; but I persist in thinking that that which we feel, when we feel, i.e. distinctly attend to, a sensation, is capable of existing when it is not felt, and does so exist in all vision, hearing, and touching of external objects. This is a realistic view of introspection which is not popular. But it rests on the principle, now at last obtaining recognition, that knowledge is of its essence adventitious to what is known; and it may appeal to the argument that, for us to know by experience that the esse of feelings is sentiri (and not, let us say, sentire), we should have, in experiencing them, to be conscious not only of the quality or state but of the consciousness, which according to James is not a datum of experience at all.
      Moreover, the facts are difficult to construe on the idealistic hypothesis. If, for instance, I allow the after-image to fall half on the thumb-nail and half on yonder wall, the part falling on the wall still appears vastly larger than the part falling on the thumb-nail; and yet it is, and can be observed to be, an exact half of the total image! I cannot persuade myself that between the time of my taking the half as a false object obscuring part of the wall, and so as different in size from the other false object, and my taking it as a sensation, it has undergone a change in size such that now the two halves are equal. It seems to me much more consonant with the facts to suppose that the size of the false object was itself false — that it was matter of imagination, or projected action, and not of sense.
      To this it may be replied — and here we come to the second objection — that the size of the false objects is felt. I am inclined to think that this objection rests on a foundation of fact. Visual distance is not a mere matter of thought or projected action, but seems to be felt; and size, which varies with distance, is consequently also felt. On the other hand, there is an unmistakable heterogeneity between distance and the other two visual dimensions, length and breadth: distance does not appear spread out before us, as length and breadth are. The following hypothesis therefore suggests itself. It is well known that the chief factor in the visual perception of distance — with the blurring caused by binocular disparity — is convergence and accommodation of the eyes. The sense that distance is actually felt may then be due to the fact that it is brought before us by the muscular sensations of convergence and accommodation. Distance, in that case, would be felt but not visually felt. And the instance would constitute a beautiful example of the way external objects and relations are known by means of sensations which have in them little of the characters of the external things, but are simply used as signs.
      These considerations contain the reply to the argument that the datum must be an existence because it is sensibly vivid. The datum is sensibly vivid, because it is brought before us by a sensation and not by a mental image, but it is not properly a sensible fact. That is, we cannot actually find it as a feeling, as we can find an emotion or a pain; we can only tend towards it or mean it. Here we come to the function of the intellect ( in a wide sense ) in connection with sense perception, which is no less important than that of sense. In other words, a meaning here is not to be understood as a peculiar kind of feeling that can be met with introspectively in the same way that a visual sensation or a pain can, but as a function which the feeling discharges in bringing us into mental relation to an external thing. When, having a sensation caused by an object in our minds, we are disposed (in virtue of the connected nervous arrangements) to act as with reference not to it but to the object, then that object is, in so far, before the mind as a datum. And it is because the datum is a functional fact that the same object may be brought before the mind with sensible vividness, by means of a sensation, as something now present, or faintly, by means of a mental image, as merely imagined. I trust I have now made out a case for the view that perceptual data must be distinguished from the sensations by the use of which they are given; that, while the sensations are in time and perhaps space, the data are not so; and that only the sensations are existences, while the data are logical entities essences.


Before drawing the consequences which follow from this view it may be worth our while to consider briefly the parallel distinction that exists in the case of memory between the datum, which here, too, will be found to be a mere essence, and the mental image by means of which the datum is given.
      It has been proved, in one of the earlier of these essays against the pragmatists, that in memory the object known cannot be identified with the idea of it which the subject has before his mind when he remembers, since it has to be admitted to be an inaccessible past fact which can only be “meant,” not directly experienced. What I shall now try to show is that this idea — if we mean by “idea” what is actually before the mind — must be recognized to be distinct from the mental image, visual, auditory, or other, by means of which we conceive it; that this mental image alone is a present fact, an existence; and that the idea is the mere character which we conceive the past fact to have, without its existence in short, an essence. If the past fact itself cannot be given in memory, and if, on the other hand, it and nothing else must somehow be seized or before us in order that there should be memory at all, then what is before us must be its character without its existence: the datum must be a mere essence.
      In the essay referred to Mr. Lovejoy argued that the datum in memory is not something merely present, but “present-as absent.” While there can be no objection to this simply as a vivid phrase or metaphor, I would point out that the word present” has at least three meanings: ( 1 ) present to me in space — “here”; ( 2 ) present in time, and not past or future — “now”; ( 3 ) present to the mind, or “given.” The relevant meaning in the present instance is “given,” and it will be conducive to clearness of thought if we substitute this technical term for the more vague and metaphorical present,” and say that the past is “given-as-absent” — or “given-as-past.” I will not here take up the question whether the pastness is a true part of the essence given, or comes in rather through our placing of the true essence, our referring it to a particular temporal position; I shall assume, for the purposes of this argument, that it is a part of the essence.
      If, then, we try to analyse exactly what is given to us when we remember, I think we shall recognize, first, that at least there is no conscious contrasting of the past with the present no conceiving of it as being not-now, but at most a conceiving of it as then. In so far as we merely remember, we do not think of the present at all. Hence it will be better not to use the formula “given-as-absent,” which seems to imply some awareness of the relation between the past and the present, but to speak of the datum in memory as “given-as-past.” And of course we have no awareness (so far as we merely remember) that the past is given. So the true datum of memory is just simply “the past.”
      Now, how can it be maintained that this datum, this mere airy vision which must appear before the mind if we are to grasp the real past at all, is a present psychic state or existence? What is there in common (as to fundamental category) between something whose central essence is pastness, something not now real, and a visual or auditory image which is a present psychic existence? Such an image is, of course, necessary to determine what it is we remember — I must imagine the flash, if I am to remember striking a match a moment ago — but this present psychic state is the mere vehicle of the meaning “the past,” it is not itself in any way an object of awareness when we remember. Similarly, we can conceive a class of things — “man” — but the image of a particular man, Socrates or other, or the sound of the word “man” heard internally, is not the datum at the moment; the datum is “man-in-general.” In a word, we must distinguish, in memory and conception as much as in sense-perception, between the datum of the cognition, a mere essence, and the psychic state which is the vehicle of the datum.
      When once this distinction is clearly made, it becomes evident that the datum, while not identifiable with the object in this sense, that we can argue that wherever a datum appears there must be a real object and that in contemplating the datum we are actually beholding the object as an existence, is yet and must be identical with the object in this other sense, that, if the knowledge is true, the essence given is the true essence of the object — so that in contemplating the datum we virtually behold the object. How could there be knowledge at all unless we managed somehow virtually to behold absent things, to behold the past and the future, and, in the case of sense-perception, to behold objects existing separately from ourselves?
      This logical or essential identity is thus the keystone of a correct theory of knowledge; and it is the substitute we must offer for the literal and absolute identity asserted by the neo-realists and the pragmatists.


In recent American discussion the view defended by the authors of this book has been opposed, as “epistemological dualism,” to the “epistemological monism” represented especially by the neo-realists. This way of formulating the issue seems to me not in all respects happy. My colleagues have, indeed, guarded themselves carefully against being thought to advocate ontological dualism — a charge to which my way of speaking of physical things and psychic states in the preceding pages might seem to render me liable, though not with justice, since I hold that the two form a single world and that what appear to us as physical things are in them selves of psychic nature. The question I would raise is, however, whether even in epistemology the word “dualism” correctly expresses the relation between what is given and the real thing. For this is the relation which in epistemology we are especially concerned about. The physical thing and the psychic state or sensation by means of which I perceive it are unquestionably two, and mutually independent as much so as the physical thing and my organism or ego, of which the psychic state is a state. Nothing can obscure the fundamental fact that sense-perception is a means of adjusting the organism to its environment — of making the ego aware of his friends and enemies — and that the ego and the environment are two, not one. It is quite another question whether the datum, the vision of the object that is given to the ego by means of his psychic state, is distinct from the object, in such wise that the object and the essence are two. If the essence is truly the essence of the object, as it should be in order that knowledge may be correct, the essence given and the essence embodied in the object are not two but one.
      Here appears the immense advantage we have gained, in point of epistemological theory, by recognizing that the datum is a mere essence, a universal. If the datum were an existence — as it would necessarily be if its givenness were given in and with it, or if it were itself in time and space — it would necessarily be a second existence, independent of the object, and then, in being aware of it, we should not be aware of the object. It is precisely because it is a mere universal that the essence given and the essence embodied in the object may be the same, and that the mind in sense-perception may there fore be able to rest directly on the object. Hence it is only when we are wrong, and the essence given betrays or mis-presents the object, that there is epistemological dualism; when we are right, epistemological monism – in this carefully limited sense is the truth.
      The view that the datum is an existence (psychical or other) inevitably leads to the fallacy of representationism, or ( 2 ) at the beginning. Representationism is the theory that the datum is the thing primarily known, and that it represents the physical thing, as a portrait represents a person. This is very near the truth, but it subtly perverts it, in a way entailing the most disastrous consequences. A picture is a distinct existence from a person; if you see the picture, by hypothesis you do not see the person. It is another embodiment of the same essence. The consequence is that, in knowing the representative datum, you fail to know the object. This is the result of conceiving the datum as an existence, and therefore as known. Whereas, on our view, knowledge requires two things: the givenness of an essence, and affirmation — that is, acting as if the essence were embodied in a real object and mere givenness is not knowledge. The case is just like that of judgment, where a proposition must needs first be conceived before it can be affirmed.
      Representationism has proved historically, and is naturally, the half-way house to subjectivism. Convince yourself, by reflecting on the characters which we attribute to physical things, how far data fail to correspond to them, and at the same time think of data, as existences, as things primarily known, not as the mere given-essences of things known, and these data necessarily become barriers, screens, cutting us off from physical things instead of uniting us to them. The mere givenness of data becomes “experience.” Independent things can at best only be inferred from data. But by what right do we employ inference to carry us beyond experience? Inference properly conducts us only from one experienced thing to another — we find by experience that A is succeeded by B, and when A comes we infer that B will follow; it cannot carry us beyond possible or eventual experience, and assure us of the existence of something that cannot be experienced at all. This train of thought has always, and must inevitably, conduct him who conceives “experience” as the givenness of existent data, and not as the perception of real things, from representationism onward to subjectivism.
      Then follows the familiar sequence of psychological and logical subjectivism , psychological and logical objectivism. The experienced existence is at first very naturally conceived as psychological in its nature, as something whose esse is percipi, as involving givenness in its very being — as “experience. But, as philosophers reflect further upon experience, they see that in point of fact nothing psychological is given that a chick who pecks at a grain of corn is not dealing (even from his own subjective point of view) with a sensation, that we do not think of mental images or of thoughts of things but simply of things; in a word, that the datum is objective in its category, that it is a pure essence without any flavouring of givenness or the psychical. Psychological subjectivism thus perforce changes into logical subjectivism; or, in historical terms, the idealism of Berkeley, Hume, and Mill gives place to the idealism of the post-Kantians.
      Finally, in our own day, the influence of science makes itself felt in philosophy, and a system which, in defiance of Copernicus, would make the world revolve about the individual ego or an Absolute Ego difficult to distinguish from it becomes less and less credible. Idealism, it is seen, must go; but the assumption which was its fundamental premise — the identity of the given-essence with the physical thing — is still allowed to remain. The primal fallacy of the Cartesian “ideal theory,” in other words, has not yet been exorcised. Upon this basis we get, first, psychological objectivism, the doctrine that “the perception is in the object,” that the fundamental data are experienced-things (which, by a strange contradiction, continue to exist as “experienced-things” when they are not experienced); and, second, logical objectivism or neo-realism (the neo-realism of our six innovators), with its assertion that the fundamental data are “neutral things ” which are yet at the same time continuously existent physical things, a chaos of mingled hits and misses which is yet at the same time the system of reality.
      The crux of this last philosophy is the problem of error; how can things be unreal which are nevertheless real, and the only reals? The problem is an insoluble one; it can seem to be solved, only by now representing all error as intellective, as matter of interpretation, none as perceptual, and now throwing overboard the principle of contradiction. The predicament in which the logical objectivist finds himself can be escaped only by recognizing that data as such are not existences or reals, and that the existence of real things is not given but only affirmed.
      To sum up, error of perception (i.e. colour-blindness, hallucination, dreaming, the existence of secondary qualities) is possible only because the givenness of the essence is independent of its embodiment, in such wise that an essence may be given different to a greater or less extent from that which is embodied. This possibility is secured by the psychological mechanism of sense-perception, which uses states of the ego as symbols to bring before us objects, i.e. to make essences given. Truth of perception is possible only because the essences given are not existences, but universals, the bare natures (if they are the natures) of the objects, in such wise that the essence embodied and the essence given may be the same. This combination of psychological duality with logical unity is therefore the very essence of the epistemological situation. Only by recognizing that data are as we have described them can the pitfalls and snares of the question be avoided, and a solution be reached which places knowing on a healthy common-sense basis. If, and only if, the datum is a mere logical vision of the real thing can it truly be a vision of it.

1 As I have elsewhere explained, I owe this precious conception to Mr. Santayana. I had long been convinced that cognition requires three categories for its adequate interpretation; the intermediate one — between subject and object — corresponding to the Kantian “phenomenon” or “appearance.” At one time I used to designate this category as “content,” since it agrees with the current conception of a “content of consciousness”; but, in my efforts to conceive it clearly, I was continually falling off either into the category of “object” or into that of “psychic state.” What was my relief when at last I heard Mr. Santayana explain his conception of “essence,” and it dawned upon me that here was the absolutely correct description of the looked-for category.