The Validity of External Sense-Knowledge

Place of External Sensation in Knowledge

At the outset, the student of Criteriology should impress this fact upon his mind and memory: there can be no knowledge in the intellect that has not in some manner come from external sensation. There have been philosophers in the remote past, and a few in relatively recent times, who taught that our ideas and judgments, or some of them, are born in us. This theory of inborn ideas is called Innatism (from Latin in-natus, “born in”). The theory has been refuted time and again from Aristotle onwards. Scholasticism rejects it as false. Among non-Scholastics who have ably refuted it, John Locke (1632-1704) stands eminent.

Our knowledge begins with external sensation; from sense-data the mind abstracts ideas, and employs the ideas in judgments and reasonings. This does not mean that knowledge of the mind is of the same essential order as that of the external senses. Intellectual knowledge is not merely a refined or elaborated sensation. It is a different sort of knowledge. But the mind does get its “materials” from the senses, and uses its native power of abstraction to draw from these materials its understanding of the essences of things. So the mind, in a true sense, depends upon the external (and internal) senses; not, indeed, in its being or powers, but in the circumstances of this life, in which soul and body are joined in a single human substance.

Man has no direct contact with outer reality except the senses. Only when these have functioned, can the mind (in this union of soul and body) go into action and exercise its power of apprehending things. Thus, ideas are not inborn, but are formed by the intellect from the findings of sense. St. Thomas translates an expression of Aristotle to describe the mind of man before he has had any sense-experience: he calls such a mind tabula rasa, that is, a slate upon which nothing has as yet been written.

It is not necessary to undertake a long or involved argument in refutation of Innatism. Most modern philosophers are quite at one with us in regarding it as a fallacious theory. But we must briefly notice its inadequacy.

Innatism is a gratuitous theory, that is to say, it is presented without any show of real proof. Indeed, it is impossible to formulate a direct argument for Innatism. New-born babies can give us no evidence, and the memory of adults is powerless to recall the experiences of infancy. On the other hand, ideas are amply accounted for in the activity of sense, plus the abstractive function of the mind. Study of the mental processes and states gives evidence that all ideas, even those of things that lie beyond the grasp of sense, are the product of sensation, plus mental abstraction. The doctrine of Innatism is, therefore, not required to explain ideas. On the contrary, it conflicts with the findings of introspection and study of the knowingprocesses. For these reasons we find Innatism inadmissible.

All knowledge, then, begins with external sensation. It is to the external senses, therefore, that we turn first when we take up the study of the validity of human knowledge.

Requisites for Validity in Sense-knowledge

The senses give us knowledge of things in the material world about us. Knowledge of extra-organic objects is mediate, for it is effected in the subject by the medium of intra-organic objects, but the intraorganic object is not recognized as a medium of knowledge, and its very existence is unknown, until it is discovered by scientific investigation of the sensing-process.

For external sensation, the outer or trans-subjective object must be impressed upon the organ of sense. This impressed object is taken into the organ physically and so becomes intra-organic. It is the intra-organic object that is immediately sensed. We learn things “as they are” (that is, as they exist for normal experience, not in their atomic and sub-atomic structure) by the action and experience of the several senses and by the check-up which such experience affords. This check-up and extended experience is called mediate experience, and it is by means of it that we gain our perfect sense-knowledge of the material world about us.

The object of the external senses must be transsub jective in matter, form, and presence. This is required by the very nature of external sensation. Such sensation is not creative; it does not produce its object, but apprehends it. Nor does it clothe its object in a mode or form of singular and concrete existence; the object has such a mode of existence. Nor does external sensation project its object by evoking an image; its object is there, localized within the range of the sense which it affects.

For valid sensation, it is obvious that the senses must be normally and perfectly constituted. Not that a person imperfectly endowed in point of senses can gain no true knowledge, but such a person has to make continuous correction through mediate experience before he can be certain of the findings of senses even moderately defective, and if some sense be lacking, he can have no perfect knowledge of the proper object of that sense at all. When we ask whether knowledge of the senses is valid and true knowledge to be relied upon with certitude, we must surely consider such knowledge as is gained by senses which are organically sound. This is a prime requisite. Secondly, judgment on the validity of sense-knowledge would be unfair, were the senses to be judged by the data which come through them, but do not constitute their proper object. The second requisite, then, is that the sense, which is to be judged as to validity, be engaged upon its proper object. The third requisite is that the organically perfect sense be engaged upon its proper object under due conditions and in a proper medium for the exercise of the sense. Obviously, it would not be a fair judgment of sense-validity to judge of sight, for example, when the organ is much fatigued or used in insufficient light.

To sum up: for validity of sense-knowledge, the perfectly sound sense must be engaged upon its proper object, which is truly trans-subjective in matter, form, and presence, and which falls within proper 192 x CERTITUDE range of the sense under due conditions and in a proper medium for the action of the sense.

When the requirements indicated are met, senseknowledge is valid and infallible. This point will engage our attention in the next section of this article.

C) SENSE-KNOWLEDGE IS VALID Our senses give us knowledge of an external world.

They do not create this world, but apprehend it. Now, sense-knowledge is basically valid if the external world is there. And sense-knowledge is thoroughly valid if the external world is there as known to the sentient subject through the mediate experience of the senses, external and internal.

Is the external world there? Some philosophers have taught that it is a projection of the ego, that the sentient subject is the creator of his world, or is merely an element in some general “awareness” which belongs to an Absolute Being. To admit such a theory is to lapse at once into Universal Skepticism, which, as we have seen elsewhere, is a wholly impossible doctrine, essentially self-contradictory. The skeptic has no right to speak and to argue; such action would suppose the existence of what he is concerned to deny, and would surrender his whole position ; the skeptic can only settle into eternal silence.

Things about us in the world are there. We do not create the world by projecting it out of ourselves in a series of “externalizations.” To say so would be to declare the world a world of dreams. Nay, it would be to declare the dreamer himself a part of his dream.

Yet everyone makes a clear distinction between himself and the thing he knows. The veriest subjectivist will admit that his knowing is not the object of his sensation. He will admit that the eye does not see itself seeing, nor the ear hear itself hearing. He will admit that the eye does not see sound, nor the ear hear color. He will, in short, admit that the knowingprocess of external sensation perceives proper objects as things distinct from the knower and his senses.

Now, if this be mere seeming, upon what sort of argument are we to base our acceptance of it as seeming? The person whose theory contradicts universal experience is in the position of the defender of a thesis. It is “up to him” to make good his position.

And one may rather pity him in his futile attempt to offer argument to the unreal projections of his own ego. On our part, we have sound and sufficient reasons for rejecting the “appearance theory.” For consider: if the objects of external sensation are not really trans-subjective, then they must be subjective, they must be internal to the knower. And the knower himself, is he trans-subjective to another knower who knows him? If so, his theory falls. If not, his own existence as a sense-endowed being is the projection of some knower. Of whom or what? Of himself?

The thought is impossible; it involves a “short circuit” and an annihilation of this theory and all others.

Of something else? But that something else must be trans-subjective, and again the thesis falls. The subjectivist may insist that he and the objects of external sensation are but the projections of something unknown and unknowable. But this is Agnosticism, which, as we have seen, is a theory wholly untenable, and, in the present case, amounts to Universal Skepticism.

If there be no “externality” in the objects of external sensation, how is it possible even to know what external and externality mean ?

If we assume with Huxley that the ego is a thing partly conscious and partly unconscibus, and that the unconscious part projects itself and the conscious part is aware of the projections as the external world, we face insuperable difficulties. How shall we account for the strange conduct of the unconscious ego? It is certainly part and parcel of the subject. What drives it to the amazing feat of presenting itself as its opposite, that is, as objective (trans-subjective) when it is really subjective? The theory is gratuitous and whimsical.

Again, if we regard the world about us as a mythworld, how shall we explain the general acceptance of it as a real world ? Some philosophers have taught that we regard things about us as existent and real because we have acquired the habit of doing so. How, then, did this habit originate ? A habit results from repeated acts. The first “externalizations” must have been effected without the aid of any habit at all. How did they come to be made? The original question returns.

The theories, therefore, which deny real transsubjectivity to the objects of external sensation all lead to absurdities and contradictions. We must reject them as inadmissible.

On the positive side, we call upon experience for our argument. When we undergo the thing called external sensation, we are aware that we do not so much act as receive; we are aware that we are acted upon. True, we know that we ourselves do the sensing, but we are also aware that the thing sensed is not produced by ourselves, but is there to be sensed.

When I speak to a friend whom I meet casually in the street, I am aware that it is really I that see him and hear his voice replying to my greeting. Awhile since, I did not see him; now I do see him. A moment ago I did not hear his voice; now I do hear it. Something not myself, something trans-subjective, has obtruded itself upon my external senses of sight and hearing; something has come to me from the outer world of the non-ego. My friend was not here before me; now he is here before me. This thing has happened to me.

It is a thing I did not foresee, a thing I did not conjure up, a thing I did not produce. It is a thing that came objectively into the range of my senses and impressed itself upon them.

The external senses, therefore, do not produce their object. They do not produce the thing that is their object; that is to say, their object is transsub jective in matter. The external senses do not invest their object with a mode of being; they apprehend the object as a concrete, singular, material reality, and this is the mode which things in nature must have; that is to say, the external senses have an object that is trans-sub jective in form. The external senses do not evoke images of objects that have been sensed and held somehow as retained experiences to be projected in image; the object must be here and now present within the range of the sense which perceives it; that is to say, the external senses have an object that is trans-subjective in presence.

The object of the external senses is, therefore, wholly and perfectly trans-subjective. External sensation is, in consequence, based upon the most solid grounds of reality. External sensation is valid. Of course, imperfections in sense-organs, imperfections in the medium in which the senses work, disproportion in the objects sensed, and so on, may lead to mistakes and errors. But the error will always be found to be an error of judgment. One errs because one judges precipitately, and without taking into account the imperfections mentioned. When due allowance is made for these, when the check-up of mediate experience is applied, then even imperfect sensingpowers may give grounds for valid judgments and for true and certain knowledge.

Granted that the senses grasp objects that are really there, it may be asked, Do the senses grasp objects as they are in nature? It is hardly fair to put the question in this form. Certainly, the sense of sight, for instance, is not equipped for microscopic work. I look at a glass of clear water; it seems to have perfect transparency and translucency. I say that there is nothing in the water, it is free from extraneous objects. But any drop of that clear water, when put under a powerful microscope, will disclose multitudes of tiny bodies that are not water. Therefore, may I say that my eyes deceive me? Not at all.

No more than I could say that my ears deceive me because they do not bring me all the sounds that are made in a city a hundred miles away. When I ask whether the senses grasp objects as they are, I mean to ask whether they grasp objects as presented to their normal apprehending power. My answer to that query is affirmative. The senses do grasp their objects as presented.

Again, in asking whether the senses grasp their objects as they are in nature, I must recall that most sensations are complex; they are composed of several percepts of different senses. My morning cup of coffee appears to sight as a dark brown object; to smell it offers a special and peculiar aroma; to touch it offers resistance and temperature; to taste it offers a distinctive flavor. By the union of the percepts of sight, smell, touch, and taste, I know coffee as it is in nature. But strictly, I do not see coffee; I see that it is colored. I do not smell coffee; I smell its aroma.

I do not touch coffee, but touch makes me aware of its resistance and temperature. I do not taste coffee; I taste its flavor. Hence, I may be deceived (but not by my sense of sight) if I judge a certain liquid to be coffee, whereas it is not coffee at all. Some practical joker may put into the cup on my breakfast-table a liquid that has the color of coffee, and I do not discover that it is not coffee until I have had the experience (probably unpleasant) of tasting it. My judgment is erroneous; my sense of sight is not. I see what is there; I see the colored object. If the circumstances of the occasion impel me to a wrong judgment, it is in judgment that I err, not in sensation.

I judge upon the percept of sight, whereas judgment cannot be delivered safely except upon the combined percepts of sight, taste, smell, and touch. Even then, a “coffee-substitute” might be near enough in flavor and aroma, in color and temperature, to deceive me, and to make me judge the object to be coffee, whereas it is not. But the senses do not deceive; they perceive what is there; if the combination of percepts that I have learned to know as coffee is approximated closely enough to make me judge as coffee a liquid that is something else, the combination of percepts is still valid; I do perceive this combination of color, aroma, flavor, heat, and temperature; I do perceive what is there. My judgment is wrong, but my senses are not; and judgment could be corrected only upon authority (of the cook or the manufacturer of the coffee-substitute) or upon investigation of the ingredients of the coffee-substitute. Similarly, when I mistake a man for his twin, my senses are not deceived; I mistake in judgment. The senses perceive the thing that is there, as presented.

Therefore, we may not give a direct and unexplained answer to the question, “Do the external senses perceive things as they are?” We must first distinguish the proper object of each sense; and we can answer that a sense perceives its proper object as presented. We must also assert the complexity of objects known by sense, and indicate the combination of various percepts that enter into a thing known. We indicate the error that is very likely to occur if one judges on a single one of these percepts without taking all the others into consideration. But such error of judgment is capable of correction.

Judgment can be made safely and soundly when due allowances are made, and from the valid findings of sense, valid knowledge is acquired.

We know, therefore, by the action of external senses the object as presented. This knowledge is direct, immediate, accurate grasp of the intra-organic object. That, of course, is the meaning of the phrase, “as presented”; it means, as intra-organically impressed. Our knowledge of the extra-organic world as such is mediate.

The extra-organic objects that make up the bodily world are presented to the external senses as really extra-organic, but not until the sentient subject has had some experience, especially through the sense of touch, with things about him in this world. A newborn baby will reach for the moon as readily as for the lamp or candle close at hand. Nor is this a question of mere distance. It is a question of knowing the outer or extra-organic object as such. The baby has not* had the experience of repeated actions and applications of touch to enable it to judge the localization of the object. It merely sees the bright object—the moon or the lighted lamp. It is in no way enabled by vision to judge the intra-organic object as such, nor the extra-organic object as such. It merely grasps thexobject. To know the extra-organic object as such requires the “mediate experience” of which we have spoken. This mediate experience comes of the fact that the internal senses of memory and imagination are led by different external sensations that occur together, and again occur separately, to a kind of association and severance of sensiles, and so recognize one sensile as calling for, or excluding, another. Thus one learns to associate the sound which one hears with the bell which one sees swinging, perfume with the flower, depth and distance with the colored surface perceived by sight.

Thus sound and perfume and color are apprehended as extra-organic, as outside the body and apart from the organ of the sentient subject. Even touch and taste do not perceive their object as extra-organic until the sentient subject has been schooled by “mediate experience” to recognize it so. This experience enables the subject to distinguish the taste-contacts and touch-contacts as changeable and occasional, and thus as different from the permanent inner contacts of parts of the sentient body. So the outer object which comes in contact with the sentient body through taste or touch is distinguished from the body itself. A new-born baby which suffers pain from some outer contact (from touching a very hot object, for example, or from tasting a bitter medicine) will experience the pain and will cry. But the baby will not localize the cause of the pain as an outer (extra-organic) object, nor will it make a conscious withdrawal from the painful contact. Mediate sensile experience has not yet enabled the child to make distinction between the intra-organic and the extra-organic object. By mediate sensile experience we distinguish the object as intra-organically presented, from the outer or extra-organic object as the latter is in itself. We learn this from such facts as these: that sounds die away or increase, that odors weaken, that colors, shapes, and sizes vary, that temperatures change. Imagination (which preserves and reproduces the images of past experience) is, so to speak, the repository of mediate sensile experience, and it corrects or checks external sensations and enables the subject to apprehend the extraorganic object as it is in nature. So, by the power of imagination, the intra-organic object (which is in itself an imperfect image of the extra-organic object) becomes perfect, and faithfully represents the extra-organic object as it is in sensible nature. When thus, by mediate experience, the extra-organic object is known as such—as it is in itself—then the intra-organic object is also known as such, but implicitly and confusedly. known. Clear and distinct recognition of the intra-organic object as such is the fruit of scientific investigation.

The extra-organic object, then, is known as such by the aid of mediate experience. Now, the basis of all mediate experience is the sense of touch. The simple touch-sensation does not, indeed, enable the subject to know the object as distinct from his own body. But repeated and varied contacts soon force the subject to recognize this distinction. And upon this distinction, as upon a firm basis and foundation, reposes the knowledge of other outer objects as outer, as extra-organic.

The external senses, therefore, can and do give us a valid knowledge of things. External sensation is a true source of certitude.

Our argument is based, of course, upon the uniformity of nature. But this uniformity must be admitted. Those who would deny it make all science impossible and involve themselves in contradictions that carry them at once into Universal Skepticism.

And against the convinced universal skeptic, there is no argument available. Such a skeptic admits no certainty. Were he to argue, he would admit the existence of himself and of his opponent; he would admit a valid reasoning power in himself by which he would frame his argument, and he would admit an equally valid reasoning power in his opponent, who would be expected to understand the argument.

In a word, were the universal skeptic to utter the slightest defense of his position, he would be no longer a skeptic, but a dogmatist. All who take up the investigation of the validity of knowledge must admit, to begin with, the existence and uniformity of nature and must proceed perforce upon that assumption. Now, if nature is uniform and consistent, as sane apprehension shows it to be, then the senses, equipped with organs which are manifestly constructed and marvellously adapted to perform a certain function, must really perform that function.

Therefore, if nature is consistent, and not vain or deceiving (and if nature were that, we would be plunged into the intellectual despair and ultimate insanity of Universal Skepticism), then the senses, properly constructed and used under due conditions, are the source of reliable knowledge, of certitude.

But errors, as we have said, do occur. We have instanced errors, and have given the obvious explanation of them as errors, not of sense, but of judgment on sense-findings. It may be well to mention an additional error or two by way of further illustration.

Looking at a spoon partly immersed in water, one sees the spoon as bent or broken. Removing the spoon from the water, one sees that it is not bent or broken. Is sight deceived? No. Sight has for its proper object colored surface, not shape. If the colored surface of the visible object is presented partly through one medium (air) and partly through another medium (air and water), it is still true that the sense of sight perceives its object as presented, that is, perceives it truly as intra-organically impressed. But if one bases judgment as to shape upon the finding of sight, without taking into account the variance in medium, and without the check-up of touch (to which shape appeals as a common sensile as well as to sight), then the judgment is apt to be erroneous. The error is accidental, not essential; that is, the error comes from precipitate and illconditioned judgment on sense-findings, and not from sense-findings themselves. Checking up on the shape of the spoon by the sense of touch, one is able to make correction of the accidental error of judgment based on sight alone, and so to achieve true knowledge of the object.

Again: approaching the golden dome of St.

Peter’s Basilica from the west on a late summer afternoon, one sees the dome as silvery. Is sight deceived? Not so. The error is accidental. The object as presented to sight is truly seen. The special angle of sunlight produces an effect of silver, and the effect is really there. Under that precise light, the object is really silvery. Add to the angle of light, the distance of the object from the beholder, and the effect of intervening atmosphere. Check this effect by a nearer view under a different light, and the erroneous judgment, “That is a silver dome,” will be corrected. Mediate experience enables one to learn the object as it is in sensible nature.

Let the student consider the following instances of erroneous judgment on sense-findings, and let him explain the error as accidental and not essential to sense as such:

1. A man buys a scarf in a shop lighted by electric lights. He examines the scarf and finds it a solid black in color. Later, in daylight, he discovers that the scarf is deep blue.
2. The characters in a “talking picture” appear to move and to talk. Investigation shows that the reel consists of hundreds of motionless photographs, and that the sound does not come from the pictured actors at all.
3. A straight line with sloping projections at the ends looks longer than an equal line without the projections.
4. Hearing the booming of the great bell in the church tower at Notre Dame University, one close at hand senses a continuous roar, while one two miles distant hears distinct bell-strokes.
5. An oculist places his patient in a dark room and turns on a tiny light fifteen feet away from the patient’s eyes. The oculist then places a red lens over the left eye, and a clear lens over the right eye. Presently the patient sees two lights, one red, one white.

Summary Of The Article

In this lengthy article we have discussed the importance of the knowledge of the external senses in any study of the validity of human knowledge. We have seen that the theory of Innatism, or inborn knowledge, is to be rejected, and that all human knowledge rests upon the foundation of external sensation. We have listed the requisites for validity in sensation. We have discussed the subject of validity in sensation, and have found that the senses give us true and reliable knowledge, and are therefore a source of certitude. We have seen that error in sensation is accidental, and that it is always error of judgment, and not error of sense as such.