Brown Thomas
Lectures on the Philosophy of the Human Mind (Vol. 1 of 3)
If, indeed, the appearance of the brain and nerves were such, as marked them to be peculiarly fitted for the communication of motion of any sort, there might be some presumption, from this very circumstance, in favour of the opinion, that sensation takes place, only after a progressive series of affections of some sort, propagated along the nerve to the interior brain. But it must be remembered, that the nature, both of the substance of the nerves themselves, and of the soft and lax substance, in which they are loosely embedded, renders them very ill adapted for the communication of nice varieties of motion, and gives some additional likelihood, therefore, to the supposition, that affections of the sensorial organ, so distinct as our sensations are from each other, and so exactly corresponding with the slightest changes of external objects, do not depend on the progressive communication of faint and imperceptible motion, in circumstances so unfavourable to the uninterrupted progress even of that more powerful motion, which can be measured by the eye. In a case so doubtful as this, however, in which the intervening changes supposed by philosophers, – if such a progressive series of motions do really take place, – are confessed to be beyond our observation, it is impossible for any one, who has a just sense of the limits, which nature has opposed to our search, to pronounce with certainty, or even perhaps with that faint species of belief, which we give to mere probability. My conjectures on the subject, therefore, I state simply as conjectures, and nothing more.
If, indeed, what is but a mere conjecture could be shown to be well founded, it would add another case to the innumerable instances, in which philosophers have laboured, for ages, to explain what did not exist, – contenting themselves, after their long toil, with the skill and industry which they have exhibited, in removing difficulties, which they had before, with great skill and industry, placed in their own way. “I am not so much convinced of our radical ignorance,” says an ingenious writer, “by the things that are, of which the nature is hid from us, as by the things that are not, of which notwithstanding we contrive to give a very tolerable account; for this shews that we are not merely without the principles which lead to truth, but that there are other principles in our nature, which can accommodate themselves very well, and form a close connexion, with what is positively false.”
But whatever reason there may be for removing this supposed link of the corporeal part of the process of sensation, there is another prior link, which it appears to me of great importance to separate from the chain. I allude to the distinction, which is commonly made, of the objects of sense, as acting themselves on our organs, or as acting through what is termed a medium.
“A second law of our nature,” says Dr Reid, “regarding perception is, that we perceive no object, unless some impression is made upon the organ of sense, either by the immediate application of the object, or by some medium which passes between the object and the organ. In two of our senses, to wit, touch and taste, there must be an immediate application of the object to the organ. In the other three, the object is perceived at a distance, but still by means of a medium, by which some impression is made upon the organ. The effluvia of bodies drawn into the nostrils, with the breath, are the medium of smell; the undulations of the air, are the medium of hearing; and the rays of light passing from visible objects to the eye, are the medium of sight. We see no object, unless rays of light come from it to the eye. We hear not the sound of any body, unless the vibrations of some elastic medium, occasioned by the tremulous motion of the sounding body, reach our ear. We perceive no smell, unless the effluvia of the smelling body enter into the nostrils. We perceive no taste, unless the sapid body be applied to the tongue, or some part of the organ of taste. Nor do we perceive any tangible quality of a body, unless it touch the hands, or some part of our body.”71
It is evident, that, in these cases of a supposed medium, which Dr Reid considers as forming so important a distinction of our sensations, the real object of sense is not the distant object, but that which acts immediately upon the organs, – the light itself, not the sun which beams it on us, – the odorous particles, which the wind has wafted to us from the rose, not the rose itself upon its stem, – the vibrations of the air, within our ear, not the cannon that is fired at the distance of miles. The light, the odour, the vibrating air, by which alone our senses are affected, act on our nerves of sight, of smell, and hearing, with an influence as direct, and as little limited in the kind of action, as that with which the fruit, which we eat or handle, acts on our nerves of taste or touch. This influence of the objects immediately external is all, in which our organs of sense, and consequently the mind as the principle of mere sensation, is concerned. The reference to the distant sun, or rose, or cannon, which alone leads us to speak of a medium in any of these cases, is the effect of another principle of our intellectual nature, – the principle of association, or suggestion, – that is afterwards to be considered by us, without which, indeed, our mere transient sensations would be comparatively of little value; but which, as a quality or susceptibility of the mind, is not to be confounded with that, by which the mind becomes, instantly sentient, in consequence of a certain change produced in the state of its sensorial organ.
Since, however, precisely the same series of changes must take place in nature, whether we class the sun, the flower, the cannon, as the objects of sense, or merely the light, the odorous particles, and the vibrating air, it may perhaps be thought, that the distinction now made is only a verbal one, of no real importance. But it will not appear such to those who are conversant with the different theories of perception which we are afterwards to review; many of which, that have had the greatest sway, and a sway the most fatal to the progress of intellectual philosophy, appear, to me, to have arisen entirely, or at least chiefly, from this very misconception as to the real external object of sense. It is sufficient at present to allude to the effect, which the mere distance of the supposed object must have had, in giving room to all the follies of imagination to fill up the interval.
It may be necessary, however, to remark by the way, that though I do not conceive the bodies which act through a medium, as it is said to be the real objects of the particular sense; – the immense orb of the sun, for example, in all its magnitude, to be the object of that small organ by which we are sensible of light; or the cannon, which exists we know not where, to be the object of that organ by which we are sensible of sound; – I am still far from objecting to the popular and very convenient phraseology, by which we speak of seeing the sun, and hearing the cannon – a phraseology that expresses briefly a reference, which could not otherwise be expressed but by a very awkward circumlocution, and to make any innovation in which would be as absurd, as to reject the popular phrases of the sun's rising and setting merely because they are inconsistent with our astronomical belief. The most rigid philosophy can require no more, than that, when we talk of the sun's actual setting, we should mean by it, only a certain position relative to that great luminary at which the earth arrives in its diurnal revolution, – and that, when we talk of seeing it descend, we should mean nothing more, than that we see light of a certain brilliancy, from which we infer the existence and relative position of the orb that has projected it.
I have been led into these observations, on the various parts of the corporeal process which precedes sensation, by the desire of removing, as much as possible, any obscurity in which your notions on the subject might be involved, – as I know well the influence which even a slight confusion in our notion of any part of a complicated process has, in spreading, as it were, its own darkness and perplexity over parts of the process, which otherwise we should have found no difficulty in comprehending. You might think, that you knew less distinctly the mental sensation itself, because you knew only obscurely the series of bodily changes that precede sensation; but still it must be remembered, that it is only the last link of the corporeal chain, – the ultimate affection of the sensorial organ, in whatever manner and to whatever extent it may be affected, – immediately antecedent to the affection of the mind, which is to be considered as that with which nature has united the corresponding change in our mental frame. This mysterious influence of our bodily on our mental part has been poetically compared to that which the sun was supposed to exercise on a lyre, that formed part of a celebrated Egyptian statue of Memnon, which was said to become musical when struck with its beams; and though the poet has extended the similitude, beyond our mere elementary sensations, to the complex perception of beauty, it is still a very happy illustration – as far as a mere poetic image can be an illustration – of the power which matter exercises over the harmonies of mind: —
“For as old Memnon's image, long renown
By fabling Nilus, to the quivering touch
Of Titan's ray with each repulsive string
Consenting, sounded through the warbling air
Unbidden strains, – even so did Nature's hand,
To certain species of external things
Attune the finer organs of the mind.
So the glad impulse of congenial powers,
Or of sweet sound, or fair proportion'd form,
The grace of motion, or the bloom of light,
Thrills through Imagination's tender frame,
From nerve to nerve. All naked and alive,
They catch the spreading rays; till now the soul
At length discloses every tuneful spring,
To that harmonious movement from without.
Responsive. Then the charm, by Fate prepar'd
Diffuses its enchantment.72 Fancy dreams
Of sacred fountains, and Elysian groves,
And vales of bliss! the Intellectual Power
Bends from his awful throne a wondering ear,
And smiles; the Passions, gently soothed away,
Sink to divine repose; and Love and Joy
Alone are waking.”73
When we consider the variety of our feelings thus wonderfully produced, – the pleasures, and, still more, the inexhaustible knowledge, which arise, by this mysterious harmony, from the imperceptible affection of a few particles of nervous matter, it is impossible for us not to be impressed with more than admiration of that Power, which even our ignorance, that is scarcely capable of seeing any thing, is yet, by the greatest of all the bounties of heaven, able to perceive and admire. In the creation of this internal world of thought, the Divine Author of our being has known how to combine infinity itself with that which may almost be considered as the most finite of things; and has repeated, as it were, in every mind, by the almost creative sensibilities with which He has endowed it, that simple but majestic act of omnipotence, by which, originally, He called from the rude elements of chaos, or rather from nothing, all the splendid glories of the universe.
LECTURE XX
PARTICULAR CONSIDERATION OF OUR SENSATIONS. – NAMELESS TRIBES OF SENSATIONS – SENSATIONS OF SMELL – OF TASTE – OF HEARING
A considerable portion of my last Lecture, Gentlemen, was employed in illustrating the corporeal part of the process of perception, which, though less immediately connected with our Science than the mental part of the process, is still, from its intimate connexion with this mental part, not to be altogether neglected by the intellectual inquirer. The importance of clear notions of the mere organic changes is, indeed, most strikingly exemplified in the very false theories of perception which have prevailed, and in some measure still prevail; and which evidently, in part at least, owe their origin to those confused notions, to which I alluded in my last Lecture, of the objects of perception, as supposed to operate at a distance through a medium, and of complicated series of changes supposed to take place in the nerves and brain.
In considering the Phenomena of our Mind, as they exist when we are capable of making them subjects of reflection, I mentioned to you, in a former Lecture, that although we have to encounter many additional difficulties, in consequence of early associations, that modify forever after our original elementary feelings, with an influence that is inappreciable by us, because it is truly unperceived, there are yet some advantages, which though they do not fully compensate this evil, at least enable us to make some deduction from its amount. The benefit to which I allude, is found chiefly in the class of phenomena which we are now considering, – a class, indeed, which otherwise we should not have regarded as half so comprehensive as it truly is, since, but for our previous belief of the existence of a permanent and independent system of external things acquired from other sources, we should have classed by far the greater number of the feelings, which we now refer to sense, among those which arise spontaneously in the mind, without any cause external to the mind itself.
Though the sensations, which arise from affections of the same organ – as those of warmth and extension for example, or at least the feeling of warmth and a tactual feeling, that is commonly supposed to involve extension, from affections of the same nerves of touch, – are not, in every case, more analogous to each other, than the sensations which arise from affections of different organs, – and though, if we were to consider the sensations alone, therefore, without reference to their organs, we might not form precisely the same classification as at present, – the division, according to the organs affected, in most cases corresponds, so exactly, with that which we should make, in considering the mere sensations as affections of the mind, and affords in itself a principle of classification, so obvious and definite, that we cannot hesitate, in preferring it to any other which we might attempt to form. In the arrangements of every science, it is of essential consequence, that the lines of difference, which distinguish one class from another, should be well marked; and this advantage is peculiarly important in the science of mind, the objects of which do not, as in the other great department of nature outlast inquiry, but are, in every case, so very shadowy and fugitive, as to flit from us, in the very glance, that endeavours to catch their almost imperceptible outline.
In examining, then, according to their organs, our classes of sensation; and considering what feelings the organic affections excite at present, and what we may suppose them to have excited originally, – I shall begin with those which are most simple, taking them in the order of smell, taste, hearing, – not so much, from any hope, that the information, which these afford will throw any great light on the more complex phenomena of sight and touch, as because the consideration of them is easier, and may prepare you gradually for this difficult analysis, which awaits us afterwards, in the examination of those more perplexing phenomena.
I begin, then, with the consideration of that very simple order of our sensations which we ascribe to our organ of
SMELL
The organ of smell, as you well know, is principally in the nostrils, – and partly also in some continuous cavities on which a portion of the olfactory nerves is diffused.
Naribus interea consedit odora hominum vis
Docta leves captare auras, Panchaia quales
Vere novo exhalat, Floræve quod oscula fragrant
Roscida, cum Zephyri furtim sub vesperis hora
Respondet votis, mollemque aspirat amorem.74
When the particles of odour affect our nerves of smell, a certain state of mind is produced, varying with the nature of the odoriferous body. The mere existence of this state, is all the information which we could originally have received from it, if it had been excited previously to our sensations of a different class. But, with our present knowledge, it seems immediately to communicate to us much more important information. We are not merely sensible of the particular feeling, but we refer it, in the instant, – almost in the same manner, as if the reference itself were involved in the sensation, – to a rose, hemlock, honeysuckle, or any other substance, agreeable or disagreeable; the immediate presence, or vicinity of which we have formerly found to be attended with this particular sensation. The power of making the reference, however, is unquestionably derived from a source different from that, from which the mere sensation is immediately derived. We must previously have seen, or handled, the rose, the hemlock, the honeysuckle; or if, without making this particular reference, we merely consider our sensation of smell as caused by some unknown object external to our mind, we must at least have previously seen or handled some other bodies, which excited, at the same time, sensations analogous to the present. If we had been endowed with the sense of smell, and with no other sense whatever, the sensations of this class would have been simple feelings of pleasure or pain, which we should as little have ascribed to an external cause, as any of our spontaneous feelings of joy or sorrow, that are equally lasting or equally transient. Even at present, after the connexion of our sensations of a fragrance with the bodies which we term fragrant, has been, in a great measure, fixed in our mind, by innumerable reflections, we still, if we attend to the process of the reference itself, are conscious of a suggestion of remembrance, and can separate the sensation, as a mere feeling of the mind, from the knowledge of the object or external cause of the sensation, which seems to us a subsequent state of the mind, however close the succession may be. Indeed, what is there which we can discover, in the mere sensation of fragrance, that is itself significant of solidity, extension, or what ever we may regard as essential to the existence of things without? As a mere change in the form of our being, it may suggest to us the necessity of some cause or antecedent of the change. But it is far from implying the necessity of a corporeal cause; – any more than such a direct corporeal cause is implied in any other modification of our being, intellectual or moral, – in our belief, for example, of the most abstract truth, at which we may have arrived by a slow developement of proposition after proposition, in a process of internal reflective analysis, – or in the most refined and sublime of our emotions, when, without thinking of any one of the objects around, we have been meditating on the Divinity who formed them – himself the purest of spiritual existences. Our belief of a system of external things, then, does not, as far as we can judge from the nature of the feelings, arise from our sensations of smell, more than from any of our internal pleasures or pains; but we class our sensations of smell as sensations, because we have previously believed in a system of external things, and have found, by uniform experience, that the introduction of some new external body, either felt or seen by us, was the antecedent, of those states of mind which we denominate sensations of smell, and not of those internal pains or pleasures, which we therefore distinguish from them, as the spontaneous affections of our own independent mind.
ON TASTE
With the organ of taste you are all sufficiently acquainted. In considering the phenomena, which it presents, in the peculiar sensations that directly flow from it, it is necessary to make some little abstraction from the sensation of touch, which accompanies them, in consequence of the immediate application of the tangible sapid body to the organ; but the sensations, thus co-existing, are so very different in themselves, as to be easily distinguishable. When the organ of taste is in a sound state, the application of certain substances produces, immediately, that change or affection of the sensorial organs, which is attended with a corresponding change or affection of the sentient mind. In our present state of knowledge, we immediately refer this simple sensation, to something, which is bitter, or sweet, or acrid, or of some other denomination of sapid quality; and we have no hesitation, in classing the sensations as sensations, – effects of laws of action that belong jointly to matter and mind, – not as feelings that arise in the mind, from its own independent constitution. But, if we attend sufficiently to the feeling that arises in the case of taste, we shall find, however immediate the reference to a sapid body may seem to be, that it is truly successive to the simple sensation, and is the mere suggestion of former experience, when a body previously recognized by us as an external substance, was applied to our organ of taste; – in the same manner, as, when we see ashes and dying embers, we immediately infer some previous combustion, which we could not have inferred, if combustion itself had been a phenomenon altogether unknown to us. In the simple sensation which precedes the reference, – the mere pleasure of sweetness or the mere pain of bitterness – there is nothing which seems to mark more distinctly the presence of honey or wormwood, or any similar external substance, than in any of our joys or sorrows, to which we have not given a name; and there can be no doubt, that, if the particular feeling which we now term joy, and the particular feeling which we now term sorrow, had been excited, whenever we knew, from other sources, that certain bodies were applied to the tongue, we should have considered these internal feelings as sensations, in the strict sense of the word, precisely in the same manner, as we now regard, as sensations, the feeling which we term sweetness, and the feeling which we term bitterness, because, like these sensations, they could not have failed to suggest to us, by the common influence of association, the presence and direct coincidence of the object without. In the case of taste, therefore, as in the case of smell, we could not, from the simple sensations, – if these alone had been given to us, – have derived any knowledge of an external world, of substances extended and resisting; but we consider them as sensations, in the strict philosophic meaning of the term, because we have previously acquired our belief of an external world.
It may be remarked of these two classes of sensations, now considered, that they have a greater mutual resemblance, than our sensations of any other kind. It is only a blind man who thinks, that what is called scarlet is like the sound of a trumpet; but there are tastes which we consider as like smells, in the same manner as we consider them to be like other tastes; and, if we had not acquired a distinct knowledge of the seats of our different organs, and had yet known that smells and tastes arose from external causes acting upon some one or other of these, we should probably have been greatly puzzled, in many cases, in our attempt to refer the particular sensation to its particular organ.
In considering the advantages which we derive from our organs of smell and taste, the mere pleasures which they directly afford, as a part of the general happiness of life, are to be regarded, from their frequent occurrence, as of no considerable amount. The fragrance of the fields enters largely into that obscure but delightful group of images, which rise in our minds on the mere names of spring, summer, the country, and seems to represent the very form of ethereal purity, as if it were the breath of heaven itself.
If we imagine all the innumerable flowers which nature pours out, like a tribute of incense to the God who is adorning her, again to be stripped, in a single moment, of their odour, though they were to retain all their bright diversities of colouring, it would seem as if they were deprived of a spirit which animates them, – how cold and dead would they instantly become, – and how much should we lose of that vernal joy, which renders the season of blossoms almost a new life to ourselves.
“In vain the golden Morn aloft
Waves her dew-bespangled wing;
With vermeil cheek and whisper soft
She woos the tardy Spring;
Till April starts, and calls around
The sleeping fragrance from the ground,”75
It is by this delightful quality that the tribes of vegetable life seem to hold a sort of social and spiritual communion with us. It is, as it were, the voice with which they address us, and a voice which speaks only of happiness. To him who walks among the flowers which he has tended,
“Each odoriferous leaf,
Each opening blossom, freely breathes abroad
Its gratitude, and thanks him with its sweets.”
The pleasures of the sense of taste, in the moderate enjoyment of which there is nothing reprehensible, are, in a peculiar manner, associated with family happiness. To have met frequently at the same board, is no small part of many of the delightful remembrances of friendship; and to meet again at the same board, after years of absence, is a pleasure that almost makes atonement for the long and dreary interval between. In some half-civilized countries, in which the influence of simple feelings of this kind is at once more forcible in itself, and less obscured in the confusion of ever varying frivolities and passions, this hospitable bond forms, as you well know, one of the strongest ties of mutual obligation, sufficient often to check the impetuosity of vindictive passions which no other remembrance could, in the moment of fury, restrain. Had there been no pleasure attached to a repast, independent of the mere relief from the pain of hunger, the coarse and equal food would probably have been taken by each individual apart, and might even, like our other animal necessities, have been associated with feelings which would have rendered solitude a duty of external decorum. It would not be easy, even for those who have been accustomed to trace a simple cause through all its remotest operations, to say, how much of happiness, and how much even of the warm tenderness of virtue, would be destroyed, by the change of manners, which should simply put an end to the social meal; that meal which now calls all the members of a family to suspend their cares for a while, and to enjoy that cheerfulness, which is best reflected from others, and which can be permanent only when it is so reflected, from soul to soul, and from eye to eye.
One very important advantage, more directly obvious than this, and of a kind which every one may be disposed more readily to admit, is afforded by our senses of smell and taste, in guiding our selection of the substances which we take as alimentary. To the other animals, whose senses of this order are so much quicker, and whose instincts, in accommodation to their want of general language, and consequent difficulty of acquiring knowledge by mutual communication, are providentially allotted to them, in a degree, and of a kind, far surpassing the instincts of the slow but noble reflector man, these senses seem to furnish immediate instruction as, to the substances proper for nourishment, to the exclusion of those which would be noxious. To man, however, who is under the guardianship of affections more beneficial to him than any instinct of his own could be, there is no reason to believe, that they do this primarily, and of themselves, though, in the state in which he is brought up, instructed with respect to every thing noxious or salutary, by those who watch constantly over him in the early period of his life, and having, therefore, no necessity to appeal to the mere discrimination of his own independent organs, and, still more, as in the artificial state of things, in which he lives, his senses are at once perplexed and palled, by the variety and confusion of luxurious preparation, it is not easy to say, how far his primary instincts, – if it had not been the high and inevitable dignity of his nature to rise above these, – might, of themselves, have operated as directors. But, whatever their primary influence may be, the secondary influence of his organs of taste and smell is not the less important. When we have once completely learned what substances are noxious, and what are salutary, we then, however similar they may be in their other sensible qualities, discriminate these as often as they are again presented to us, by that taste or smell, which they affect with different sensations; and our acquired knowledge has thus ultimately, in guiding our choice, the force and the vivacity of an original instinct.
HEARING
In considering the phenomena of the sense of hearing, to which I now proceed, I may apply to them the same remark, which has been already applied to the phenomena of the senses before considered. They are classed by us, as sensations, merely in consequence of our previous belief in the existence of those external bodies, the motion of which we have known to be followed by similar feelings. Our mind begins suddenly to exist in a certain state; and we call this state joy or sorrow, without supposing that it depends on the immediate presence of any external object. It begins again to exist, in a different state, and we say, that we hear a flute, referring the feeling immediately to an external cause. But there can be no doubt, that, in making this reference, in the one case, and not in the other, we are influenced by experience, and by experience alone. If we suppose ourselves endowed with the single sense of hearing, and incapable therefore of having previously seen or felt the flute, which is breathed before us, or any other extended and resisting object whatever, we may imagine the mere sound to recur, innumerable times, without discovering any mode by which it can give us more knowledge, than we should receive from a similar recurrence of any internal joy or sorrow. That we should be able to refer it to a body, such as we now mean, when we speak of a flute, is manifestly impossible; since this implies knowledge of solidity, and form, and colour, which could not be acquired without touch and sight. But there seems even no reason to think, that we should refer it to any external cause whatever, unless, indeed, such a reference necessarily accompanied every feeling, which we know is far from being the case, since we have many internal pleasures, not more like to each other, than they are to the sound of a flute, which we do not refer to any thing, separate or separable, from the constitution of our own mind. In hearing, therefore, as in taste and smell, we do not derive from its sensations our knowledge of things external, but, in consequence of our knowledge of things external, we regard these feelings, as sensations, in the common philosophic meaning of that term.