The Essays of Adam Smith: ADAM SMITH ON THE EXTERNAL SENSES - Of the Sense of HEARING.

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Of the Sense of HEARING.

EVERY sound is naturally felt as in the Ear, the organ of Hearing. Sound is not naturally felt as resisting or pressing upon the organ, or as in any respect external to, or independent of, the organ. We naturally feel it as an affection of our Ear, as something which is altogether in our Ear, and nowhere but in our Ear, or in the principle of perception which feels in our Ear. We soon learn from experience, indeed, that the sensation is frequently excited by bodies at a considerable distance from us; often at a much greater distance, than those ever are which excite the sensation of Smelling. We learn too from experience that this sound or sensation in our Ears receives different modifications, according to the distance and direction of the body which originally causes it. The sensation is stronger, the sound is louder, when that body is near. The sensation is weaker, the sound is lower, when that body is at a distance. The sound, or sensation, too undergoes some variation according as the body is placed on the right hand or on the left, before or behind us.

In common language we frequently say, that the sound seems to come from a great or from a small distance, from the right hand or from the left, from before or from behind us. We frequently say too that we hear a sound at a great or small distance, on our right hand or on our left. The real sound, however, the sensation in our ear, can never be heard or felt any where but in our ear, it can never change its place, it is incapable of motion, and can come, therefore, neither from the right nor from the left, neither from before nor from behind us. The Ear can feel or hear nowhere but where it is, and cannot stretch out its powers of perception, either to a great or to a small distance, either to the right or to the left. By all such phrases we in reality mean nothing but to express our opinion concerning either the distance or the direction of the body which excites the sensation of sound.

When we say that the sound is in the bell, we do not mean that the bell hears its own sound, or that any thing like our sensation is in the bell, but that it possesses the power of exciting that sensation in our organ of Hearing. Though in this, as well as in some other cases, we express by the same word, both the Sensation, and the Power of exciting that Sensation; this ambiguity of language occasions scarce any confusion in the thought, and when the different meanings of the word are properly distinguished, the opinions of the vulgar, and those of the philosopher, though apparently opposite, on examination turn out to be exactly the same.

These four classes of secondary qualities, as philosophers have called them, or to speak more properly, these four classes of Sensations; Heat and Cold, Taste, Smell, and Sound; being felt, not as resisting or pressing upon the organ, but as in the organ, are not naturally perceived as external and independent substances; or even as qualities of such substances; but as mere affections of the organ, and what can exist nowhere but in the organ.

They do not possess, nor can we even conceive them as capable of possessing, any one of the qualities, which we consider as essential to, and inseparable from, external solid and independent substances.

First, They have no extension. They are neither long nor short; they are neither broad nor narrow; they are neither deep nor shallow. The bodies which excite them, the spaces within which they may be perceived, may possess any of those dimensions; but the Sensations themselves can possess none of them. When we say of a Note in Music, that it is long or short, we mean that it is so in point of duration. In point of extension we cannot even conceive, that it should be either the one or the other.

Secondly, Those Sensations have no figure. They are neither round nor square, though the bodies which excite them, though the spaces within which they may be perceived, may be either the one or the other.

Thirdly, Those Sensations are incapable of motion. The bodies which excite them may be moved to a greater or to a smaller distance. The Sensations become fainter in the one case, and stronger in the other. Those bodies may change their direction with regard to the organ of Sensation. If the change be considerable, the Sensations undergo some sensible variation in consequence of it. But still we never ascribe motion to the Sensations. Even when the person who feels any of those Sensations, and consequently the organ by which he feels them, changes his situation, we never, even in this case, say, that the Sensation moves, or is moved. It seems to exist always, where alone it is capable of existing, in the organ which feels it. We never even ascribe to those Sensations the attribute of rest; because we never say that any thing is at rest, unless we suppose it capable of motion. We never say that any thing does not change its situation with regard to other things, unless we can suppose it to be capable of changing that situation.

Fourthly, Those Sensations, as they have no extension, so they can have no divisibility. We cannot even conceive that a degree of Heat or Cold, that a Smell, a Taste, or a Sound, should be divided (in the same manner as the solid and extended substance may be divided) into two halves, or into four quarters, or into any number of parts.

But though all these Sensations are equally incapable of division; there are three of them, Taste, Smell, and Sound; which seem capable of a certain composition and decomposition. A skilful cook will, by his taste, perhaps, sometimes distinguish the different ingredients, which enter into the composition of a new sauce, and of which the simple tastes make up the compound one of the sauce. A skilful perfumer may, perhaps, sometimes be able to do the same thing with regard to a new scent. In a concert of vocal and instrumental music, an acute and experienced Ear readily distinguishes all the different sounds which strike upon it at the same time, and which may, therefore, be considered as making up one compound sound.

Is it by nature, or by experience, that we learn to distinguish between simple and compound Sensations of this kind? I am disposed to believe that it is altogether by experience; and that naturally all Tastes, Smells, and Sounds, which affect the organ of Sensation at the same time, are felt as simple and uncompounded Sensations. It is altogether by experience, I think, that we learn to observe the different affinities and resemblances which the compound Sensation bears to the different simple ones, which compose it, and to judge that the different causes, which excite those different simple Sensations, enter into the composition of that cause which excites the compounded one.

It is sufficiently evident that this composition and decomposition is altogether different from that union and separation of parts, which constitutes the divisibility of solid extension.

The Sensations of Heat and Cold seem incapable even of this species of composition and decomposition. The Sensations of Heat and Cold may be stronger at one time and weaker at another. They may differ in degree, but they cannot differ in kind. The Sensations of Taste, Smell, and Sound, frequently differ, not only in degree, but in kind. They are not only stronger and weaker, but some Tastes are sweet and some bitter; some Smells are agreeable, and some offensive; some Sounds are acute, and some grave; and each of these different kinds or qualities, too, is capable of an immense variety of modifications. It is the combination of such simple Sensations, as differ not only in degree but in kind, which constitutes the compounded Sensation.

These four classes of Sensations, therefore, having none of the qualities which are essential to, and inseparable from, the solid, external, and independent substances which excite them, cannot be qualities or modifications of those substances. In reality we do not naturally consider them as such; though in the way in which we express ourselves on the subject, there is frequently a good deal of ambiguity and confusion. When the different meanings of words, however, are fairly distinguished, these Sensations are, even by the most ignorant and illiterate, understood to be, not the qualities, but merely the effects of the solid, external, and independent substances upon the sensible and living organ, or upon the principle of perception which feels in that organ.

Philosophers, however, have not in general supposed that those exciting bodies produce those Sensations immediately, but by the intervention of one, two, or more intermediate causes.

In the Sensation of Taste, for example, though the exciting body presses upon the organ of Sensation, this pressure is not supposed to be the immediate cause of the Sensation of Taste. Certain juices of the exciting body are supposed to enter the pores of the palate, and to excite, in the irritable and sensible fibres of that organ, certain motions or vibrations, which produce there the Sensation of Taste. But how those juices should excite such motions, or how such motions should produce, either in the organ, or in the principle of perception which feels in the organ, the Sensation of Taste; or a Sensation, which not only does not bear the smallest resemblance to any motion, but which itself seems incapable of all motion, no philosopher has yet attempted, nor probably ever will attempt, to explain to us.

The Sensations of Heat and Cold, of Smell and Sound, are frequently excited by bodies at a distance, sometimes at a great distance, from the organ which feels them. But it is a very ancient and well-established axiom in metaphysics, that nothing can act where it is not; and this axiom, it must, I think, be acknowledged, is at least perfectly agreeable to our natural and usual habits of thinking.

The Sun, the great source of both Heat and Light, is at an immense distance from us. His rays, however (traversing, with inconceivable rapidity, the immensity of the intervening regions), as they convey the Sensation of Light to our eyes, so they convey that of Heat to all the sensible parts of our body. They even convey the power of exciting that Sensation to all the other bodies that surround us. They warm the earth and air, we say; that is, they convey to the earth and the air the power of exciting that Sensation in our bodies. A common fire produces, in the same manner, all the same effects; though the sphere of its action is confined within much narrower limits.

The odoriferous body, which is generally too at some distance from us, is supposed to act upon our organs by means of certain small particles of matter, called Effluvia, which being sent forth in all possible directions, and drawn into our nostrils by the inspiration of breathing, produce there the Sensation of Smell. The minuteness of those small particles of matter, however, must surpass all human comprehension. Inclose in a gold box, for a few hours, a small quantity of musk. Take out the musk, and clean the box with soap and water as carefully as it is possible. Nothing can be supposed to remain in the box, but such effluvia as, having penetrated into its interior pores, may have escaped the effects of this cleansing. The box, however, will retain the smell of musk for many, I do not know for how many years; and these effluvia, how minute soever we may suppose them, must have had the powers of subdividing themselves, and of emitting other effluvia of the same kind, continually, and without any interruption, during so long a period. The nicest balance, however, which human art has ever been able to invent, will not show the smallest increase of weight in the gold box immediately after it has been thus carefully cleaned.

The Sensation of Sound is frequently felt at a much greater distance from the sounding, than that of Smell ever is from the odoriferous body. The vibrations of the sounding body, however, are supposed to produce certain correspondent vibrations and pulses in the surrounding atmosphere, which being propagated in all directions, reach our organ of Hearing, and produce there the Sensation of Sound. There are not many philosophical doctrines, perhaps, established upon a more probable foundation, than that of the propagation of Sound by means of the pulses or vibrations of the air. The experiment of the bell, which, in an exhausted receiver, produces no sensible Sound, would alone render this doctrine somewhat more than probable. But this great probability is still further confirmed by the computations of Sir Isaac Newton, who has shown that, what is called the velocity of Sound, or the time which passes between the commencement of the action of the sounding body, and that of the Sensation in our ear, is perfectly suitable to the velocity with which the pulses and vibrations of an elastic fluid of the same density with the air, are naturally propagated. Dr. Benjamin Franklin has made objections to this doctrine, but, I think, without success.

Such are the intermediate causes by which philosophers have endeavoured to connect the Sensation in our organs, with the distant bodies which excite them. How those intermediate causes, by the different motions and vibrations which they may be supposed to excite on our organs, produce there those different Sensations, none of which bear the smallest resemblance to vibration or motion of any kind, no philosopher has yet attempted to explain to us.

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Smith, Adam. 2018. The Essays of Adam Smith. Urbana, Illinois: Project Gutenberg. Retrieved May 2022 from https://www.gutenberg.org/files/58559/58559-h/58559-h.htm#page445a

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