Fundamental Philosophy, Vol. I (of 2)

81. In order that sight may originate the idea of a solid, it requires motion. This motion is an indispensable condition, though it may be either in the object or in the eye itself.

Let us suppose an immovable eye, and see how by the motion of the objects, the sensation of sight may present or produce the idea of a solid. The only difficulty is to show how it can add to the two dimensions which constitute the plane, the third which forms the solid.

Let a fixed eye be directed to a point where there is a right rectangular parallelopipedon B, so placed that its two bases are wholly concealed, and let the right line drawn from the centre of the eye to the edge of the parallelopipedon divide the plane angle into two equal parts. Let us also suppose the sides of the parallelopipedon to be of different colors, – white, green, red, and black. In this case, the eye sees the two planes as one, and the edge appears as a right line separating the two parts of the same plane which differ only in color. It is impossible for it to conceive the inclination of the two planes, because as it refers the object to the extremity of the visual ray, and has not been able to compare the varieties which result from difference of position and distance, and from the manner in which the object receives the light, it can only distinguish the different parts of the same plane.

It is well known that perspective can perfectly imitate a solid. For, if instead of the solid B, we suppose two planes exactly representing the two sides seen, the sensation will be the same, the illusion complete. Therefore, there are two distinct ways of producing the same sensation; and consequently, unless there has been a previous comparison, there is no means of distinguishing them apart; but the idea which would naturally result would be the most simple; that is, the idea of a plane.

82. If we suppose the parallelopipedon B to revolve on a vertical axis, it will present the four planes successively to the eye, and they will appear greater or less according to their inclination to the visual ray, the surface of the plane reaching its maximum when perpendicular to the ray, and its minimum when parallel to it.

The succession and variety of the sensations will immediately produce the idea of motion; for the same planes of the parallelopipedon are seen in different positions. The uniform manner in which these planes succeed one another, will also suggest the idea that the green which appears a few moments after the black, is the same which was seen a few moments before; and so of the other colors. Also, as one is constantly hiding behind the other, this naturally gives rise to the idea of extension in the direction, or continuation of the visual ray; and this is sufficient to produce the idea of size or of a solid. When we see a plane we have the two dimensions which constitute a surface; to form the idea of a solid, we need only the idea of one dimension more; this can not be found in the same plane, but is produced by the motion of the parallelopipedon.

83. This motion which we have supposed to be around a vertical axis, we may equally suppose to take place around a horizontal axis. We shall then see in succession the two opposite sides, and the bases of the parallelopipedon with different appearances, according to their various positions; or, in other words, according to the angle formed by the planes and the visual ray. These appearances will help more and more to form the idea of the third dimension, which is not to be found in the primitive plane, and consequently to supply what was wanted to constitute the idea of a solid.

84. Just as we have supposed the eye fixed and the object movable, we may suppose the eye in motion and the object immovable. The result is the same; for, it is evident that if the eye should move around the parallelopipedon, now vertically, and now horizontally, it would experience the same sensations as when it was quiet, and the parallelopipedon moved. Thus, although we suppose the subject wholly deprived of the sense of touch, so as to be unable to perceive its own motion, it can still form the idea of solid by the impressions of sight alone. True, it could distinguish which moved, the eye or the object, but this does not interfere with the formation of the idea composed of the three dimensions.

CHAPTER XV.

SIGHT AND MOTION

85. I said that the observer could not distinguish between his own motion and that of the object; sight alone can not give us a true idea of motion. Thus in a boat, although we are certain that we are moving, the motion seems to us to be in the objects along the shore. Also if the motion of the object and that of the observer are simultaneous, in the same direction, and with the same velocity, all appearance of motion is lost. But if there are two objects, one of which moves in the same direction as ourselves, and the other in the opposite direction, we perceive only the latter. Thus in a canal boat, the horse which walks on the bank in the same direction which the boat follows, seems to move without advancing. Of the two motions of the horse, we perceive only the vertical, the horizontal escapes us.

The reason of this is clear, we can judge the object only by our impressions. When the impression varies, we have the idea of motion; but not otherwise. When the object or the eye is in motion, there is a succession of impressions on the retina, from which the idea of motion arises. But if the motion of the eye accompanies the motion of the object, one cancels the other, the impression on the retina is constant, and the object does not seem to move.

86. In the same manner if the motion of the object and that of the eye are simultaneous, but of unequal velocity, we perceive only the difference; that is to say, if the motion of the eye be represented by 3 and that of the object by 5, the motion of the object will appear as 2, or the difference between 5 and 3. If our motion is more rapid than the motion of the object, although in the same direction, the object will appear to move in the opposite direction, as when we sail down a river faster than the current, the water seems to flow backwards. An immovable object at the same time seems to move in a direction opposite to our own with greater velocity than the current; for, here also, of the two motions we perceive only the difference. The motion of the boat, which is equal to 5, seems transferred to the fixed object, which appears to move in the opposite direction with the velocity represented by 5; and if we suppose the velocity of the current to be equal to 3, it will have the appearance of moving backwards with a velocity of 5-3, or 2.

87. From these considerations it would seem to follow that although sight is sufficient to give us the idea of motion, it is not sufficient to enable us to distinguish our own motion from that of the object, but for this we have need of touch. But this is not so; for by sight alone, we can distinguish the motion of the eye from that of the object, and if in some cases this is impossible, the same is true of touch.

We must observe that in the above examples touch is of much less use than sight in order to preserve us from illusions. How by the aid of touch alone could we perceive the motion of a boat gliding smoothly down a river? Sometimes by the help of sight we observe this motion, especially if we regard the objects along the bank which we pass; but touch is essentially limited to what affects the body immediately, and therefore cannot discover motion when the body is not affected by it.

It is also well to observe that we do not refer the motion perceived by touch to the objects around us until after we have acquired this habit by means of repeated comparisons. When for the first time the hand is passed over an object, we are unable to tell whether the hand moves over the body, or the body under the hand.

The reason of this is that the sensation of motion is essentially a successive sensation, and this succession exists equally whether the hand moves or the object. Let us suppose the hand to pass along an object of a varied surface, we shall experience the variety of sensations corresponding to the surface; suppose now that the hand remains motionless, and the object passes under it with the same velocity, pressure, and friction, the sensations will be the same as before. Every one must have observed that when leaning on a slippery object, it is often difficult to tell whether it is the object which moves, or ourselves. Therefore touch also confirms what we have advanced, that the distinction between the motion of the member and that of the object does not arise from simple sensation.

88. In this respect, therefore, touch does not help sight; let us see if sight alone can enable us to distinguish between the motion of the eye and that of the object. We have already observed that a single sensation with respect to one object only is insufficient, but there is no difficulty in proving that this result may be obtained by the comparison of different sensations.

Let us suppose the eye at a point A, looking at an object B; the object will appear at the extremity of the range of the sight as if projected on a plane. To be more definite we will imagine the object B to be a column in the middle of a large hall, and the point A a corner of the same hall. The column will appear to the eye to be a part of the opposite wall. If the eye changes its position, the column will appear in another part of the wall; so that if the eye should pass around the column, it would appear successively on every part of the wall. The same succession of phenomena would be observed if the eye should remain fixed and the column should move around it; for it is evident that if the observer is placed in the centre of the room, and the column moves around him, the column will appear on all the parts of the opposite wall. From this we infer that only one sensation of sight, with only one object, is not enough to determine whether the eye moves or the object.

But if instead of one object we suppose several moving simultaneously, it is easy to see how the distinction of motions arises. Let us suppose that at the same time that the eye sees the column, it also sees other objects, such as chandeliers, statues, or other columns, placed between the eye and the opposite wall. If the eye moves every time the column changes its position on the opposite wall, the other columns, the chandeliers, statues, everything in the room seems to change its position; whereas, if the column moves and the eye remains fixed, the column alone changes its position, while everything else remains motionless. Therefore sight alone gives us two distinct orders of phenomena of motion:

I. The first, in which all the objects change their position.

II. The second, in which one object only changes its position.

These two orders of phenomena cannot remain unperceived; for by the help of reflection excited and enlightened by the repetition of the phenomena, we must come to the conclusion that when there is an entire and constant change of all the objects, it is not they that move, but the eye; and that when only one or a part of the objects change their position, the rest remaining fixed, it is not the eye that moves, but the objects which change their position. When everything around us changes we infer that it is the eye that moves; when one or two change their position we conclude that they move and not the eye. This is not merely a supposition, it is the reality. The ideas derived from touch are essentially limited, and it is therefore impossible that they should proceed from distant objects which cannot be touched.

89. I believe I have demonstrated that the pretended superiority of touch is without foundation, and that the opinion which makes this the basis of our knowledge of external objects, the touch-stone of the certainty of the sensations transmitted by the other senses, is an error. Without it we can acquire the certainty of the existence of bodies; without it we can form the idea of surfaces and solids; without it we discover motion, and distinguish the motion of the object from that of the organ which receives the impression. The theory of sensation here explained, and the results which are deduced from the relations of the dependence or independence of the phenomena among themselves, and with our will, may all be applied to the sight as well as to the touch.

90. Summing up all we have said, we have the following results:

I. We distinguish sleep from waking, even abstracting the objectiveness of the sensations.

II. We distinguish two orders of phenomena of sensation; – the one internal, the other external, here also abstracting their objectiveness.

III. The senses give us certainty of the existence of bodies.

IV. Sensations have no type in the external object of what they represent, except extension and motion.

V. Touch is not the basis or touch-stone of certainty.

VI. All that we know by means of the senses may be reduced to this; that there are external beings, that is to say, beings placed outside of ourselves, which are extended, subject to necessary laws, and which produce in us the effects which we call sensations.

CHAPTER XVI.

POSSIBILITY OF OTHER SENSES

91. Lamennais writes: "Who can say that a sixth sense would not disturb the harmony of the others by a contrary impression? On what foundation could he deny it? If we suppose other senses different from those which nature gave us, might not our sensations and our ideas be different? Perhaps a slight modification in our organs would be sufficient to ruin our whole science. Perhaps there are beings so organized that their sensations are wholly opposed to ours, and what is true for us is false for them, and reciprocally. For, if we examine the matter closely, what necessary connection is there between our sensations and the reality? And if there were such a connection, how could the senses make it known to us?"38

The questions which these words raise are of the highest importance and merit a serious examination.

92. Is there any intrinsical impossibility of an organization different from ours, and an order of sensations different from those which we experience? It seems not; and if this impossibility exists, it is unknown to man.

Whatever opinion we adopt as to the manner in which external objects act upon the soul by means of the organs of the body, there is no necessary relation, nor even analogy, between the object and the effect which it produces in us.

A body receives upon its surface rays of the fluid which we call light, these rays are reflected upon the retina, which is another surface in communication with the brain. So far all is well, and easily understood. There is a fluid which moves, goes from one surface to another, and may cause this or that purely physical effect on the cerebral matter; but what connection is there between this and the impression of a distinct order which we call seeing, an impression which is neither the fluid nor the motion, but an affection of which the living and thinking being, the me is intimately conscious?

If, instead of the luminous fluid and its mechanism, we suppose another, as, for example, the air which vibrates upon the tympanum, what essential reason is there why this should not produce a sensation similar to that of sight? It must be confessed that it is impossible to assign an essential reason. To one who has no idea of our present organization, both phenomena are equally incomprehensible.

93. What has been said of sight and hearing may be applied to the other senses. In all there is a bodily organ affected by a body; we see the surfaces placed one before or under the other, we see motions of one kind or another; but how can we pass over the immense distance which separates these physical phenomena from the phenomenon of sensation? For my part, I see no way to do it; this point is a barrier to the human intellect; all appearances indicate that there is no connection between these two orders of phenomena except what the will of the Creator has freely established; if there is any necessary connection, this necessity is a secret to man. Examine the textures which receive the impression of the objects, the material substance which composes the nervous system which is the organ of sensations, and say what relation you can find between the physical phenomena of this matter and the wonderful harmony of sensible phenomena.

94. Still greater will be the difficulty if you consider that, although protected from any injury, the organs cease to produce sensations from the moment they are deprived of communication with the substance of the brain. The phenomena of light are produced in the cavity of the skull amid the most profound darkness; and all the wonderful magic of sensations by which the magnificent spectacle of the universe is presented to our mind, which plunges the soul into raptures at the sound of music, and which produces such varied and delightful sensations of taste and odors, all arises in the brain, a whitish, rude, and unformed substance, from the appearance of which no one could imagine it destined to such noble functions.

95. Why is it that when the nerve A, in communication with the brain is affected, we experience the sensation which we call seeing, or if the nerve B is affected, the sensation which we call hearing, and so of the other senses? There may be a reason, but, at least, we do not know it; and it is probably no other than the free will of the Creator.

Here, it is true, philosophy confesses its weakness, but, at the same time, it shows its power; for it sees the immense distance which separates these phenomena, between which there can be no point of communication but what is established by the Almighty. When there are second causes, it is the merit of philosophy to discover them; but when there are none, its merit is in rising to the first cause. A confession of its ignorance is sometimes a more sublime act of reason than the impotent effort of an unbounded pride. If the perception of profound truths exalts the intellect, is not the intellect exalted in perceiving its own ignorance, which is sometimes a profound truth?

96. The existence of another sense is, then, possible; at least, we see no impossibility of it. If the deaf man who has no idea of sound, and the blind man who knows not what color is, would be foolish to deny the possibility of those sensations of which they are deprived, can we, with any more show of reason, assert the impossibility of an order of sensations different from what we possess? If we examine the system of sensations by the light of reason, we can discover no essential dependence between the sensations and their respective organs, nor between the organs and the objects and circumstances by which they are affected. Why does the impression of the light upon my eyes cause in me a particular sensation, which cannot result from the same impression on a different part of my body? Why may not the brain receive the same impression in various forms? Why must this fluid which we call light, and no other, produce the impression? Why may not this same sensation of seeing proceed equally from other affections of the brain? A violent blow on the head produces the sensation of many luminous points, whence the common expression of "seeing stars by daylight." We must confess that philosophy knows nothing of these secrets, that as yet it has not been able to penetrate them, and it can give no answer to these questions. It sees an order of facts, but no necessary connection between them, or rather, judging from its ideas of mind and body, every thing induces it to believe that these phenomena in our life depend solely on the will of our Creator.

97. If an entirely new order of sensations is possible, there may be beings with six or seven senses. The imagination cannot conceive their nature; but reason sees in them no impossibility.

CHAPTER XVII.

EXISTENCE OF NEW SENSES

98. Is it certain that we have only five ways of sensation? I have some doubts on this point. In order to present them with the greatest clearness, and solve the questions which they raise, it is well to settle the meaning of the terms.

What is sensation? In the ordinary acceptation of the word, it is the perception of the impression transmitted to us by one of the organs of the five senses. Thus understood it is clearly limited to the action of the organs, but if considered as expressing a certain class of animal phenomena, it is the experiencing of any affection produced by an impression of the organism. Even in common use the word sensation in its broadest signification is not restricted to the impressions of the five senses, and although we make a great difference between sentiment and sensation; still we are often forced to confound them, and to use the word sensation to express things which have nothing whatever to do with the five senses. Thus we say: "The news made a great sensation;" "I cannot resist the force of such strong sensations," etc., in which cases it is evident that there is no reference to seeing, hearing, smelling, tasting, or touching, but to a different order of affections of the soul.

99. I said we were forced to use the word in the broader meaning; it is the truth which forces us. For, to the eyes of philosophy, the phenomenon of sensation consists in the production in the soul of a particular affection determined by an impression on an organ; and of whatever order this affection may be, and whatever organ may be affected, the animal phenomenon is substantially the same. The difference is in the class of affections and of the organ which is their medium, the essence of the phenomenon does not change. And if by sensations we understand such distinct orders of affections as those of sight and of touch, why may we not include other impressions caused by any other organ, whatever that organ may be?

100. Whatever use we may make of the word sensation, it is certain that we experience many affections caused by organic impressions, besides those of the five senses. What are passions but affections of the soul, springing from organic impressions? Does not the mere presence of an object often excite love, anger, pity, joy, grief, and many other sentiments of the soul?

You may say there is an essential difference between the impressions of the senses and those of the passions, that the former are independent of all previous idea and reflection, which the latter more or less presuppose. Thus, when an object is present to our open eyes, we cannot but see it and always in the same manner; and yet this object will excite in us at one time one passion, at another time another, and sometimes none; and almost always with great difference in the degree of its intensity. Moreover it is not only the mere presence of the object which causes an affection, but certain conditions are necessary, for example; the remembrance of a benefit or of an injury, etc., from which it is easy to see that there is an essential difference between the two classes of impressions.

101. If we reflect well upon this objection we shall find that though it is specious and under many aspects true, it contradicts nothing which I have asserted. I did not deny that the new impressions were subject to very different conditions from those that govern the five senses; but on the contrary I have all along supposed a difference not only in the class of impressions and the diversity of the organ, but also in the manner in which the organ is affected, and the circumstances in which the sensation is produced in the soul. I only contended that the animal phenomenon was substantially the same, that we find in it the three things which constitute its nature; a corporeal object; an organ affected by this object; and an impression produced in the soul. Because this impression cannot exist without the aid of this or that idea, this or that recollection, it does not follow that the phenomenon does not exist, or that it is not the same; it is merely to impose a new condition, and nothing more.

102. But there is no necessity of admitting that some previous idea or reflection is requisite in order that the sight of the object may produce certain impressions in the soul; – daily experience proves the contrary. How is it that the presence of an object charms in an instant a tender and perhaps innocent heart? Whence then arises that sudden fascination which is preceded by no idea, accompanied by no affection, and is scarce voluntary? Not from the thought of gross enjoyments; for perhaps he of whom I speak knows not their existence until he experiences this emotion; he feels for the first time in his breast a trouble unknown before. We must therefore recur to an organic affection similar to that which we find in the other senses. Certain conditions of age and temperament may be requisite, one object may have been necessary, among a thousand, in particular circumstances, of which the soul can give no account to itself though affected by them; yet it is still true that there is an external object, an affection of the organism, and an impression in the soul, all connected together by a mysterious, but undeniable bond.