Lectures on the Philosophy of the Human Mind (Vol. 1 of 3)

by Thomas Brown

Footnotes

[87] Darwin's Botanic Garden, Canto III. v. 353–4, and 357–360.

[88] Reid's Inquiry into the Human Mind, chap. i. sect. 5.

[89] Epilogue to the Satires, Dial. II. v. 73.

[90] Three Dialogues, &c. p. 109–110.

[91] The substance of this reference occurs in the Eleventh Anniversary Discourse,—Works, v. i. p. 165–6. 4to. Edit.

[LECTURE XXIV.]

THE SAME SUBJECT, CONTINUED.

Gentlemen, having stated, in a former Lecture, the reasons which seem to show, that the origin of our notion of extension, and of the notions, which it involves, of figure, magnitude, divisibility, is not to be found in our sense of touch, I endeavoured, in my last Lecture, to trace these to their real source,—cautioning you at the same time, with respect to the great difficulty of the inquiry, and the very humble reliance, therefore, which we can have any title to put, on the results of our investigation of a subject so very obscure.

In our present circumstances, when we attempt such an investigation, it is impossible for us to derive even the slightest aid, from remembrance of our original feelings; since memory,—which afterwards can look back through so many long and busy years, and comprehend all of life, but the very commencement of it,—sees yet, in this dawn of being, a darkness which it cannot penetrate. We have already formed,—spontaneously, and without the aid of any one,—our little system of physical science, and have, in truth, enriched ourselves with acquisitions, far more important than any which we are afterwards to form, with all the mature vigour of our faculties, and all the splendid aids of traditionary philosophy,—at a time, when we seem scarcely capable of more than of breathing and moving, and taking our aliment, and when the faculties, that leave us so much invaluable knowledge, are to leave us no knowledge of the means, by which we have acquired it.

To the period of our first sensations, therefore, we cannot look back; and, hence, all which remains for us, in an inquiry of this kind, is to consider the circumstances in which the infant is placed, and to guess, as nearly as general analogy will allow us, the nature and the order of the feelings, which, in such circumstances, would arise, in a being possessing the powers and susceptibilities of man, but destitute of all the knowledge which man possesses.

In these first circumstances of life, the infant, of course, cannot know that he has a bodily frame, or a single organ of that frame, more than he can know, that there are other bodies in nature, that act upon his own; and we are not entitled to suppose,—however difficult it may be for us to accommodate our supposition to the true circumstances of the case,—that because we, the inquirers, know, that external bodies are pressing on his organ of touch, the little sensitive being is to have any knowledge, but of the mental affections, which these external bodies excite. How the knowledge of any thing more than his own mind is acquired, is, in truth, the very difficulty, which it is our labour to solve.

In conformity with this view, then,—when we look on the infant,—one of the most remarkable circumstances, which strike us, is its tendency to use its muscles, with almost incessant exercise, particularly the muscles of those parts, which are afterwards its principal organs of measurement. Its little fingers are continually closing and opening, and its little arms extending and contracting. The feelings, therefore,—whatever these may be,—which attend the progressive contraction of those parts,—and some feeling unquestionably attends the contraction in all its stages,—must be continually arising in its mind, beginning and finishing, in regular series, and varying exactly, with the quantity of the contraction.

A succession of feelings, however, when remembered by the mind, which looks back upon them, we found to involve, necessarily, the notion of divisibility into separate parts, and, therefore, of length, which is only another name for continued divisibility. Time, in short, is to our conception, a series in constant onward progress, and cannot be conceived by us, but as a progressive series, of which our separate feelings are parts; the remembrance of the events of our life, whenever we take any distant retrospect of them, being like the remembrance of the space, which we have traversed in a journey,—an indistinct continuity of length, as truly divisible, in our conception, into the separate events which we remember, as the space, which we remember to have traversed, into its separate variety of scenes.

Time, then, or remembered succession, we found to involve, not metaphorically, as is commonly said, but truly and strictly, in its very essence, the notions of length and divisibility,—the great elements of extension; and whatever other feelings may be habitually and uniformly associated with these, will involve, of course, these elementary notions.

The series of muscular feelings, of which the infant is conscious,—in incessantly closing and opening his little hand,—must, on these principles, be accompanied with the notion,—not, indeed, of the existence of his hand, or of any thing external,—but of a certain length of succession; and each stage of the contraction, by frequent renewal, gradually becomes significant of a particular length, corresponding with the portion of the series. When any hard body, therefore, is placed in the infant's hand,—though he cannot, indeed, have any knowledge of the object, or of the hand,—he yet feels, that he can no longer perform the accustomed contraction,—or, to speak more accurately,—since he is unacquainted with any parts that are contracted, he feels, that he can no longer produce his accustomed series of feelings; and he knows the quantity of contraction, which remained to be performed, or rather the length of the series, which remained to be felt. The place of this remaining length is now supplied by a new feeling, partly muscular, and partly the result of the affection of the compressed organ of touch,—and is supplied by the same feeling, at the same point of the series, as often, as he attempts to renew the contraction, while the body remains within his hand. The tactual feeling, therefore,—whatever it may be,—becomes, by this frequent repetition, associated with the notion of that particular progressive series, or length, of which it thus uniformly supplies the place; and at last becomes representative of this particular length, precisely in the same manner, as, in the acquired perceptions of vision, certain shades of colour become representative of distance, to which they have, of themselves, no resemblance or analogy, whatever; and we thus learn to feel length, as we learn to see length,—not directly by the mere affections of our tactual or visual organs, but by the associated notions which they suggest.

If time,—as perceived by us in the continued series of our feelings,—do involve conceptual length and divisibility, it seems, indeed, scarcely possible, that, in the circumstances supposed, the notions supposed should not arise,—that the infant should be conscious of a regular series of feelings, in the contraction of its fingers and arms, and yet that portions of this series should not become significant of various proportional lengths;—and, if the notion of certain proportional lengths do truly accompany certain degrees of progressive contraction, it seems equally impossible, according to the general principles of our mental constitution, that the compound tactual and muscular feeling, which must arise in every case, in which any one of these degrees of contraction is impeded, should not become associated with the notion of that particular length, of which it supplies the place, so as at last to become truly representative of it.

In this manner, I endeavoured to explain to you, how our knowledge of the mere length of bodies may have been acquired, from varieties of length that are recognized as coexisting and proximate, and are felt to unite, as it were, and terminate in our sensation of resistance, which interrupts them equally, and interrupts always a greater number of the coexisting truths, in proportion to the size of the body compressed; and, in a similar manner, our notions of the other dimensions of bodies, which are only these varieties of length in different directions. I cannot conclude this summary, however, without recalling to your attention, a very simple experiment, which I requested you to make for yourselves,—an experiment, that, even in the unfavourable circumstances in which it must now be tried, is yet, I conceive, demonstrative of the influence of mere time, as an element of that complex notion, which we have been examining, when the more rapid measurements of vision,—which are confessedly not original but acquired,—are excluded. If, in passing our finger, with different degrees of slowness or rapidity, along the same surface, with our eyes shut,—even though we should previously know the exact boundaries of the extent of surface,—we feel it almost impossible not to believe,—and but for the contrary evidence of vision, could not have hesitated a single moment in believing,—that this extent is greater or less, according as the time employed in performing exactly the same quantity of motion, with exactly the same force of pressure, on the same quantity of our organ of touch, may have been greater or less,—it must surely be admitted, that the notion of the length, which thus uniformly varies with the time, when all other circumstances are the same, is not absolutely independent of the time,—or it must, in like manner, be believed, that our notion of visual distance, which varies with the distribution of a few rays of light on the small expanse of the optic nerve, is yet independent of those faint shades of colouring, according to the mere varieties of which, it seems at one time to lay open to our view a landscape of many miles, and at another time to present to us, as it were before our very eyes, an object of scarcely an inch in diameter. The greater dimness, and diminished size of a few objects in the back ground of a picture, which is in itself one coloured plane of light, does not more truly seem to increase the line of distance of those objects, than, in the other case, the increased slowness of the motion of our hand along any surface, seems to lengthen the line which separates one of its boundaries from the other.

That we now seem to perceive extension, immediately by touch, cannot be denied; and, in a case so obscure as this,—with our very limited knowledge, and our very limited power of adding to this knowledge,—it may seem the most prudent, and perhaps even the most suitable,—as it is, without all question, by far the easiest part,—to acquiesce in the opinion, that the perception, which now seems immediate, was so originally,—that the belief of the presence of an external figured body, is, by the very constitution of our nature, attached to a certain affection of the mere organ of touch. But, since there are circumstances,—as we have seen,—which show this opinion, when very nicely examined, to be inadmissible, we may, at least, attempt to proceed a little farther, if we do this with a sufficient sense of the very great difficulty of the attempt, in relation to our power and knowledge, and consequently with a very humble assurance, as to the certainty of any opinion which we may be led to form. To know the mind well, is to know its weaknesses as well as its powers; and it is precisely in a case of this sort, that he, whose knowledge is least imperfect, will be the best judge of its imperfection, and, therefore, the least disposed to put complete reliance on it in his own speculations,—or to assert it dogmatically, when he offers it, as all opinions, on so very obscure a subject, should be offered, to the inquiry, rather than to the undoubting assent.

The analysis, I own, is one which must require a considerable effort of attention on your part, because it is truly one of the most subtile on which I could call you to enter. But you must be aware, that this subtlety is in the nature of the very inquiry itself; since it is an inquiry into the elements and progressive growth of feelings, which seem to us, at present, simple and immediate, and that the alternatives, therefore, are not those of greater or less subtlety and refinement of analysis, but of attempting the analysis, or abandoning it altogether.

Before proceeding farther, in our inquiry with respect to the origin of the notion of extension, it may, however, be of advantage, to take a short retrospect of the progress which we have already made; for, if we have found nothing more, we have, at least, as I conceive, found reason to reject a considerable part of our former belief on the subject, which, though a negative acquisition, is yet a very important one. Though we should not be able to discover the true source of the notion which we seek, it is something, at least, to know, that we have little reason to expect to find it, where we have uniformly been accustomed to seek it.

In the first place, then, we have seen the fallacy of the supposition, that our knowledge of extension may be easily accounted for, by the similarity in figure of the compressed part of the organ of touch to the compressing body, since the notion of extension is not a state of the material organ, compressed and figured, which, as mere matter, however exquisitely organized, is as little capable of this notion, as of smell, or taste, love or aversion, but, a state of the mind itself, which is susceptible of shape or pressure, being as little square, when it perceives a square, as when it perceives a circle; and any affection of which, therefore, may be supposed as much to follow any one shape, as any other shape of the mere external organ. If, indeed, as this explanation most strangely seems to assume, we could be supposed to have any previous knowledge of the shape of our organ of touch, nothing more would be necessary, for we should then have a perfect knowledge of extension, though no other extended body but our own organ of touch were in existence. To refer us to the organ is, however, only to bring the very same difficulty one step nearer, since previously to the application of an external body, the mind has as little knowledge of the shape of its organ of touch, as it has of the body compressing it; and it is manifestly most absurd, to ascribe the origin of our knowledge of extension, to our knowledge of the resemblance in figure of an external body to our organ; since this very knowledge of the resemblance must imply the previous knowledge of the figure of both, and consequently of that very extension, which, according to this supposition, must be known to us BEFORE it is known.

In the second place, we have seen, that, if the configuration of the sensorial organ were the only circumstance necessary, to induce, immediately, in mind, the notion of figure, this notion should accompany every sensation of every kind; the smell of a rose, for example, as much as the pressure of a cube or a sphere: for the nervous expansion, in the organ of smell, and in every other organ, is of a certain figure, before sensation, during sensation, and after sensation, as much as the nervous expansion of the organ of touch. And, though we were to confine ourselves wholly to this organ, the nervous matter in it is, at all times, of a certain shape, as much when there is no pressure on it, as when it is exposed to such pressure; yet the mere figure of the organ of touch, is not then accompanied with the mental notion of its figure; nor is this the case, merely when the sense is quiescent, but, in many cases, in which it is affected in the most lively manner; as, for example, when we are exposed to great cold or heat, in which cases, the shape of this very tactual organ, thus strongly affected, is as much unperceived by us, as when there is no affection of it whatever.

Lastly, which is a point of much more importance, because it has relation to the only philosophic view of touch, as the immediate organ of extension; the view, in which the mere configuration of the compressed organ, as similar to that of the compressing body, is laid out of account, and the immediate belief of extension is supposed to depend on the original constitution of the mind, by which its affections have been arranged, so as to correspond with certain affections of the bodily organs; the mental state which constitutes the perception of a square, arising immediately when the organ of touch is affected, in a certain manner, as that mental state which constitutes the sensation of the fragrance of a rose, arises immediately, when the organ of smell is affected, in a certain manner; this opinion too, philosophic as it is, compared with those which we before considered, though, in truth, it only assumes the point in question, without attempting to solve any difficulty, supposed to be connected with it, we have yet found to be as little tenable, as the opinions that suppose the mental notion of figure to depend on the peculiar figure of the compressed material organ. The consideration which, as I stated in my last Lecture, seems to me decisive on this point, is, that, if touch inform us of extension immediately, as smell informs us of fragrance, sight of colour, and hearing of sound; it must do this in every instance, without relation to particular figure, as smell, sight, and hearing, extend to all odours, hues, and sounds; for it would certainly be, as I said, a very strange abuse of the license of supposition, to imagine that we perceive a square immediately by touch, but not a circle; or a circle, but not a square; or any one figure, but not any other figure. In short, if figure be the direct primary object of touch, as sight is of vision, we should feel immediately every form impressed, as we see immediately every colour. It is only when the figures are very simple and regular, however, such as we might be supposed to have easily learned, in the same manner as we learn, visually, to judge of distances, that we are able to discover them, as it were, immediately, by touch; and, even when we are able, in this manner, to determine the species of figure, that is to say, the mere outline of a body, we are rarely able to determine the exact magnitude which that outline comprehends; yet, as our organ must be affected by each part of the compressing surface, by the central parts, as much as by the exterior parts which form its outline, and by these, as much as by the central parts; and as every feeling which the organ directly affords, must be immediate, when there is no change of the position, or other circumstances of the object, that might vary the sensation, we should, if mere touch communicated to us the knowledge supposed, be able to determine, exactly and instantly, the magnitude and figure; or, it is evident, that the determination of magnitude and figure must depend wholly, or in part, on something that is different from touch. The magnitude we are far from being able to discover exactly, even of simple figures; and when the form is very irregular, and we know nothing more, than that a certain body is pressed against our hand,—the magnitude and figure are alike difficult to be discovered; so difficult, that I may safely say, that no one, who makes the experiment, will find, on opening his eyes, that his tactual or intellectual measurement has, in any one case, been exact, or his notion of the figure half so distinct as it now is, after a single glance. Can we then think that it is by mere touch we discover figure, as exactly as by the glance of our mature vision,—that we discover it, in all its varieties, originally by touch, and as accurately at first, as after innumerable trials,—when we discover it, only in a few cases, that are previously familiar to us, and even in these very imperfectly? The determination of the form impressed, in which we are almost conscious of a sort of intellectual measurement, has surely a much greater resemblance to the perceptions, which we term acquired, than to those which are immediate. In vision, for example, when the original power of that sense has been strengthened and enriched, by the acquisitions which it is capable of receiving from other sources, we see a long line of distance before us; and the small distances with which we are familiar, we distinguish with sufficient accuracy; but, in our visual measurement of greater distances, we are almost certain to err, taking often the less for the greater, and the greater for the less. It is precisely the same in touch. When a small body, which we have never seen, is pressed upon our hand, we are able, if its surface be square, or circular, or of any other form, with which we are well acquainted, to determine its figure, without much hesitation; because we have learned, tactually, to distinguish these regular figures. But, in endeavouring to determine, in this manner, by touch alone, the figure of any irregular body, less familiar to us, though, as a direct object of sense, if touch be the sense of figure, it should be equally and as immediately tangible as the most regular form, we feel a hesitation of the same sort, as when we attempt to ascertain by our eye, the exact distance of a remote object. To know extension or figure, is to know, not one point merely in the surface of a body, but many continuous points; and if, when the surface, is circular, we know these continuous points, and their relation to each other, immediately on pressure, we must know, as immediately, the same points and their relations, though the surface comprehending them, instead of being circular, should be of an outline more irregular. We certainly cannot know this irregular surface to have any extension at all, unless we know some parts of it; and, when the pressure is uniform from every point, and the organ of touch uniform, on which the pressure is made, it would be absurd to suppose, that we know fifty, or eighty, of the hundred points which form the impressing surface, but cannot determine its figure, because we are ignorant of the twenty of fifty remaining points; when these remaining points are acting on our organ of touch, in exactly the same manner as the fifty or eighty which we know, and when, if the surface containing merely the same number of points, had been circular, or of any other single form, as familiar to us, the whole hundred points would have been known to us equally and at once.

When our perceptions of form, then, are so various and irregular, and are more or less quick and precise, exactly as the shape which we endeavour to determine, has more or less resemblance to shapes that are familiar to us, it does not seem too bold an inference to conclude, that the knowledge of figure, which, as all extension that is capable of being perceived by us, must have some boundary, is nothing more than the knowledge of extension, is not the state of mind originally and immediately subsequent to affections of our organs of touch, any more than the perception of distance is the state of mind originally and immediately subsequent to affections of our organ of sight; and the very striking analogy of these two cases, it will be of great importance for you to have constantly in view; as it will render it less difficult for you to admit many circumstances, with respect to touch, which you might otherwise have been slower to conceive. That we should seem to perceive extension immediately by touch, though touch originally, and of itself, could not have afforded this perception, will not then appear more wonderful, than the apparently immediate perception of distance by the eye, which, of itself, originally afforded us no perception of that sort; nor the impossibility of feeling a body, without the notion of it, as extended, be more wonderful than the similar impossibility of separating colour from extension, in the case of distant vision. Above all, the analogy is valuable, as shewing the closeness and indissolubleness of the union, which may be formed of feelings that have in themselves no resemblance. What common properties, could we have conceived in vision, and that absolute blindness, which has never had a single sensation from light! and, yet, it is worthy of remark, that the perceptions of the blind, in consequence of this singular power of association, form truly the most important part of those very perceptions of vision, of which, as a whole, they are unfortunately deprived. We do not merely see with our eyes, what we may have felt with our hands; but our eyes, in the act of vision, have borrowed, as it were, those very sensations.

The proof, that our perception of extension by touch, is not an original and immediate perception of that sense, is altogether independent of the success of any endeavour which may be made, to discover the elements of the compound perception. It would not be less true, that touch does not afford it, though we should be incapable of pointing out any other source, from which it can be supposed to be derived. Of the difficulty of the attempt, and the caution with which we should venture to form any conclusion on the subject, I have already spoken. But the analysis, difficult as it is, is too interesting not to be attempted, even at the risk, or perhaps I should rather say, with the very great probability, of failure.

In such an analysis, however, though we are to proceed with the greatest caution, it may be necessary to warn you, that it is a part of this very caution, not to be easily terrified, by the appearance of paradox, which the result of our analysis may present. This appearance we may be certain, that any analysis which is at all accurate must present, because the very object of the analysis is to shew, that sensations, which appear simple and direct, are not simple,—that our senses, in short, are not fitted, of themselves, to convey that information, which they now appear, and through the whole course of our memory have appeared to us instantly to convey. It is very far, indeed from following, as a necessary consequence, that every analysis of our sensations which affords a paradoxical result, is, therefore, a just one—for error may be extravagant in appearance as well as in reality. But it may truly be regarded as a necessary consequence, that every accurate and original analysis of our sensations must afford a result, that, as first stated, will appear paradoxical.

To those who are wholly unacquainted with the theory of vision, nothing certainly can seem, as first stated, more absurd than the assertion, that we see, not with our eyes merely, but chiefly by the medium of another organ, which the blind possess in as great perfection as ourselves, and which, at the moment of vision, may perhaps be absolutely at rest. It must not surprise you, therefore, though the element which seems to me to form the most important constituent of our notion of extension should in like manner, as first stated to you, seem a very unlikely one.

This element is our feeling of succession, or time—a feeling, which necessarily, involves the notion of divisibility or series of parts, that is so essential a constituent of our more complex notion of matter,—and to which notion of continuous divisibility, if the notion of resistance be added, it is scarcely possible for us to imagine, that we should not have acquired, by this union, the very notion of physical extension,—that which has parts, and that which resists our effort to grasp it.

That memory is a part of our mental constitution, and that we are thus capable of thinking of a series of feelings, as successive to each other, the experience of every moment teaches us sufficiently. This succession frequently repeated, suggests immediately, or implies the notion of length, not metaphorically, as is commonly said, but as absolutely as extension itself: and, the greater the number of the successive feelings may have been, the greater does this length appear. It is not possible for us to look back on the years of our life, since they form truly a progressive series, without regarding them as a sort of length, which is more distinct indeed, the nearer the succession of feelings may be to the moment at which we consider them, but which, however remote, is still felt by us as one continued length, in the same manner, as when, after a journey of many hundred miles, we look back, in our memory, on the distance over which we have passed, we see, as it were, a long track of which some parts, particularly the nearer parts, are sufficiently distinct, but of which the rest seems lost in a sort of distant obscurity. The line of our long journeying—or, in other words, that almost immeasurable line of plains, hills, declivities, marshes, bridges, woods,—to endeavour to comprehend which in our thought, seems an effort as fatiguing as the very journey itself—we know well, can be divided into those various parts:—and, in like manner, the progressive line of time—or, in other words, the continued succession, of which the joy, the hope, the fragrance, the regret, the melody, the fear, and innumerable other affections of the mind, were parts, we feel that we can mentally divide into those separate portions of the train. Continuous length and divisibility, those great elementary notions of space, and of all that space contains, are thus found in every succession of our feelings. There is no language in which time is not described as long or short,—not from any metaphor—for no mere arbitrary metaphor can be thus universal, and inevitable, as a form of human thought—but because it is truly impossible for us to consider succession, without this notion of progressive divisibility attached to it: and it appears to us as absurd to suppose, that by adding, to our retrospect of a week, the events of the month preceding, we do not truly lengthen the succession, as it would be to suppose, that we do not lengthen the line of actual distance, by adding, to the few last stages of a long journey, the many stages that preceded it.

It is this spreading out of life into a long expanse, which allows man to create, as it were, his own world. He cannot change, indeed, the scene of external things. But this may be said, in one sense, to be the residence only of his corporeal part. It is the moral scene in which the spirit truly dwells; and this adapts itself, with harmonious loveliness, or with horror as suitable, to the character of its pure or guilty inhabitant. If but a single moment of life,—a physical point, as it were, of the long line—could be reviewed at once, conscience would have little power of retribution. But he who has lived, as man should live, is permitted to enjoy that best happiness which man can enjoy,—to behold, in one continued series, those years of benevolent wishes or of heroic suffering, which are at once his merit and his reward. He is surrounded by his own pure thoughts and actions, which, from the most remote distance, seem to shine upon him wherever his glance can reach; as in some climate of perpetual summer, in which the inhabitant sees nothing but fruits and blossoms, and inhales only fragrance, and sunshine, and delight. It is in a moral climate as serene and cloudless, that the destined inhabitant of a still nobler world moves on, in that glorious track, which has heaven before, and virtue and tranquillity behind;—and in which it is scarcely possible to distinguish, in the immortal career, when the earthly part has ceased, and the heavenly begins.

Is it in metaphor only, that a youth and maturity, and old age of guilt, seem to stretch themselves out in almost endless extent, to that eye which, with all its shuddering reluctance, is still condemned to gaze on them,—when, after the long retrospect seems finished, some fraud, or excess, or oppression, still rises and adds to the dreadful line—and when eternity itself, in all the horrors which it presents, seems only a still longer line of the same dreadful species, that admits of no other measure, than the continued sufferings, and remembrance, and terrors that compose it!

It is a just and beautiful observation of an ancient Stoic, that time which is past is like something consecrated to the gods, over which fortune and mortality have no longer any power, and that, dreadful as it must be to the wicked, to whom their own memory is an object of terror, it still, to the virtuous, offers itself as a consolation or joy—not in single moments like the present hour, but in all that long series of years which rises before us, and remains with us at our bidding. “Ille qui multa ambitiosè cupiit, superbè contempsit, insidiosè decepit, avarè rapuit, prodigè effudit,—necesse est memoriam suam timeat. Atqui hæc est pars temporis nostri sacra ac dedicata, omnes humanos casus supergressa, extra regnum fortunæ subducta; quam non inopia, non metus, non morborum incursus exagitat. Hæc nec turbari nec eripi potest; perpetua ejus et intrepida possessio est. Singuli tantùm dies, et hi per momenta, præsentis sunt: at præteriti temporis omnes, cum jusseris aderunt, ad arbitrium tuum se inspici ac detineri patientur.”

By those, who can look back on years that are long past, and yet say, that the continued progress, or the length and the shortness of time, are only metaphorical expressions, it might be said with equal justness, that the roundness of a sphere, is a metaphor, or the angularity of a cube. We do not more truly consider the one as angular and the other as round, than we consider the time to be continuously progressive, in which we considered, first the one figure, and then the other, and inquired into the properties of each. That which is progressive must have parts. Time, or succession, then involves the very notions of longitudinal extension and divisibility, and involves these, without the notion of any thing external to the mind itself;—for though the mind of man had been susceptible only of joy, grief, fear, hope, and the other varieties of internal feeling, without the possibility of being affected by external things, he would still have been capable of considering these feelings, as successive to each other, in a long continued progression, divisible into separate parts. The notions of length, then, and of divisibility, are not confined to external things, but are involved, in that very memory, by which we consider the series of the past,—not in the memory of distant events only, but in those first successions of feeling, by which the mind originally became conscious of its own permanence and identity. The notion of time, then, is precisely coeval with that of the mind itself; since it is implied in the knowledge of succession, by which alone, in the manner formerly explained to you, the mind acquires the knowledge of its own reality, as something more than the mere sensation of the present moment.

Conceiving the notion of time, therefore, that is to say of feelings past and present, to be thus one of the earliest notions which the infant mind can form, so as to precede its notions of external things, and to involve the notions of length and divisibility, I am inclined to reverse exactly the process commonly supposed; and, instead of deriving the measure of time from extension, to derive the knowledge and original measure of extension from time. That one notion or feeling of the mind may be united indissolubly with other feelings, with which it has frequently coexisted, and to which, but for this coexistence, it would seem to have no common relation, is sufficiently shown by those phenomena of vision to which I have already so frequently alluded.

In what manner, however, is the notion of time peculiarly associated with the simple sensation of touch, so as to form, with it, the perception of extension? We are able, in the theory of vision, to point out the coexistence of sensations which produce the subsequent union; that renders the perception of distance apparently immediate. If a similar coexistence of the original sensations of touch, with the notion of continued and divisible succession, cannot be pointed out in the present case, the opinion which asserts it, must be considered merely as a wild and extravagant conjecture.

The source of such a coexistence is not merely to be found, but is at least as obvious, as that which is universally admitted in the case of vision.

Before I proceed, however, to state to you, in what way I conceive the notion to be acquired, I must again warn you of the necessity of banishing, as much as possible, from your view of the mind of the infant in this early process, all those notions of external things, which we are so apt to regard as almost original in the mind, because we do not remember the time, when they arose in our own. As we know well, that there are external things, of a certain form, acting on our organs, which are also of a certain form, it seems so very simple a process, to perceive extension—that is to say, to know that there exist without us those external forms, which really exist—that to endeavour to discover the mode, in which extension, that now appears so obvious a quality of external things, is perceived by us, seems to be a needless search, at a distance, for what is already before our very eyes. And it will be allowed, that all this would, indeed, be very easy to a mind like ours, after the acquisitions of knowledge which it has made; but the difficulty of the very question is, how the mind of the infant makes these acquisitions, so as to become like ours. You must not think of a mind, that has any knowledge of things external, even of its own bodily organs, but of a mind simply affected with certain feelings, and having nothing but these feelings to lead it to the knowledge of things without.

To proceed, then,—The hand is the great organ of touch. It is composed of various articulations, that are easily moveable, so as to adapt it readily to changes of shape, in accommodation to the shape of the bodies which it grasps. If we shut our hand gradually, or open it gradually, we find a certain series of feelings, varying with each degree of the opening or closing, and giving the notion of succession of a certain length. In like manner, if we gradually extend our arms, in various directions, or bring them nearer to us again, we find that each degree of the motion is accompanied with a feeling that is distinct, so as to render us completely conscious of the progression. The gradual closing of the hand, therefore, must necessarily give a succession of feelings,—a succession, which, of itself, might, or rather must, furnish the notion of length, in the manner before stated, the length being different, according to the degree of the closing; and the gradual stretching out of the arm gives a succession of feelings, which, in like manner, must furnish the notion of length,—the length being different according to the degree of the stretching of the arm. To those who have had opportunities of observing infants, I need not say, how much use, or rather what constant use, the future inquirer makes of his little fingers and arms; by the frequent contraction of which, and the consequent renewal of the series of feelings involved in each gradual contraction, he cannot fail to become so well acquainted with the progress, as to distinguish each degree of contraction, and, at last, after innumerable repetitions, to associate with each degree the notion of a certain length of succession. The particular contraction, therefore, when thus often repeated, becomes the representative of a certain length, in the same manner as shades of colour, in vision become ultimately representative of distance,—the same principle of association, which forms the combination in the one case, operating equally in the other.

In these circumstances of acquired knowledge,—after the series of muscular feelings, in the voluntary closing of the hand, has become so familiar, that the whole series is anticipated and expected, as soon as the motion has begun,—when a ball, or any other substance, is placed for the first time in the infant's hand, he feels that he can no longer perform the usual contraction,—or, in other words, since he does not fancy that he has muscles which are contracted, he feels that the usual series of sensations does not follow his will to renew it,—he knows how much of the accustomed succession is still remaining; and the notion of this particular length, which was expected, and interrupted by a new sensation, is thus associated with the particular tactual feeling excited by the pressure of the ball,—the greater or less magnitude of the ball preventing a greater or less portion of the series of feelings in the accustomed contraction. By the frequent repetition of this tactual feeling, as associated with that feeling, which attends a certain progress of contraction, the two feelings at last flow together, as in the acquired perceptions of vision; and when the process has been repeated with various bodies innumerable times, it becomes, at last, as impossible to separate the mere tactual feeling, from the feeling of length, as to separate the whiteness of a sphere, in vision, from that convexity of the sphere, which the eye, of itself, would have been forever incapable of perceiving.

As yet, however, the only dimension of the knowledge, of which we have traced the origin, is mere length; and it must still be explained, how we acquire the knowledge of the other dimensions. If we had had but one muscle, it seems to me very doubtful, whether it would have been possible for us, to have associated with touch any other notion than that of mere length. But nature has made provision, for giving us a wider knowledge, in the various muscles, which she has distributed over different parts, so as to enable us to perform motions in various directions at the same instant, and thus to have coexisting series of feelings, each of which series was before considered as involving the notion of length. The infant bends one finger gradually on the palm of his hand; the finger, thus brought down, touches one part of the surface of the palm, producing a certain affection of the organ of touch, and a consequent sensation; and he acquires the notion of a certain length, in the remembered succession of the muscular feelings during the contraction:—he bends another finger; it, too, touches a certain part of the surface of the palm, producing a certain feeling of touch, that coexists and combines, in like manner, with the remembrance of a certain succession of muscular feelings. When both fingers move together, the coexistence of the two series of successive feelings, with each of which the mind is familiar, gives the notion of coexisting lengths, which receive a sort of unity, from the proximity in succession of the tactual feelings in the contiguous parts of the palm which they touch,—feelings, which have before been found to be proximate, when the palm has been repeatedly pressed along a surface, and the tactual feelings of these parts, which the closing fingers touch at the same moment, were always immediately successive,—as immediately successive, as any of the muscular feelings in the series of contraction. When a body is placed in the infant's hand, and its little fingers are bent by it as before, sometimes one finger only is impeded in its progress, sometimes two, sometimes three,—and he thus adds to the notion of mere length, which would have been the same, whatever number of fingers had been impeded, the notion of a certain number of proximate and coexisting lengths, which is the very notion of breadth; and with these, according as the body is larger or smaller, is combined always the tactual affection produced by the pressure of the body, on more, or fewer, of the interior parts of the palm, and fingers, which had before become, of themselves, representative of certain lengths, in the manner described; and the concurrence of these three varieties of length, in the single feeling of resistance, in which they all seem to meet, when an incompressible body is placed within the sphere of the closing fingers,—however rude the notions of concurring dimensions may be, or rather must be, as at first formed,—seems at least to afford the rude elements, from which, by the frequent repetition of the feeling of resistance, together with the proximate lengths, of which it has become representative, clearer notions of the kind may gradually arise.

The progressive contractions of the various muscles which move the arms, as affording similar successions of feelings, may be considered in precisely the same light, as sources of the knowledge of extension; and, by their motion in various directions, at the same time with the motion of the fingers, they concur powerfully, in modifying, and correcting, the information received from these. The whole hand is brought, by the motion of the arm, to touch one part of the face or body; it is then moved, so as to touch another part, and, with the frequent succession of the simple feelings of touch, in these parts, is associated the feeling of the intervening length, derived from the sensations that accompanied the progressive contraction of the arm. But the motion is not always the same; and, as the same feeling of touch, in one part, is thus followed by various feelings of touch in different parts, with various series of muscular feelings between, the notion of length in various directions, that is to say, of length in various series commencing from one power, is obtained in another way. That the knowledge of extension, or in other words, the association of the notion of succession with the simple feelings of touch, will be rude and indistinct at first, I have already admitted; but it will gradually become more and more distinct and precise: as we can have no doubt, that the perception of distance by the eye, is, in the first stages of visual association, very indistinct, and becomes clearer after each repeated trial. For many weeks or months, all is confusion in the visual perceptions, as much as in the tactual and muscular. Indeed, we have abundant evidence of this continued progress of vision, even in mature life, when, in certain professions that require nice perceptions of distance, the power of perception itself, by the gradual acquisitions which it obtains from experience, seems to unfold itself more and more, in proportion to the wants that require it.

The theory of the notion of extension, of which I have now given you but a slight outline, might, if the short space of these Lectures allowed sufficient room, be developed with many illustrations, which it is now impossible to give to it. I must leave you, in some measure, to supply these for yourselves.

It may be thought, indeed, that the notion of time, or succession, is, in this instance, a superfluous incumbrance of the theory, and that the same advantage might be obtained, by supposing the muscular feelings themselves, independently of the notion of their succession, to be connected with the notion of particular lengths. But this opinion, it must be remarked, would leave the difficulty precisely as before; and sufficient evidence in confutation of it, may be found in a very simple experiment, which it is in the power of any one to make. The experiment I cannot but consider as of the more value, since it seems to me,—I will not say decisive, for that is too presumptuous a word,—but strongly corroborative of the theory, which I have ventured to propose; for it shows, that, even after all the acquisitions, which our sense of touch has made, the notion of extension is still modified, in a manner the most striking and irresistible, by the mere change of accustomed time. Let any one, with his eyes shut, move his hand, with moderate velocity, along a part of a table, or any other hard smooth surface, the portion, over which he presses, will appear of a certain length; let him move his hand more rapidly, the portion of the surface pressed will appear less; let him move his hand very slowly, and the length, according to the degree of the slowness, will appear increased, in a most wonderful proportion. In this case, there is precisely the same quantity of muscular contraction, and the same quantity of the organ of touch compressed, whether the motion be rapid, moderate, or slow. The only circumstance of difference is the time, occupied in the succession of the feelings; and this difference is sufficient to give complete diversity to the notion of length.

If any one, with his eyes shut, suffer his hand to be guided by another, very slowly along any surface unknown to him, he will find it impossible to form any accurate guess as to its length. But it is not necessary, that we should be previously unacquainted with the extent of surface, along which the motion is performed; for the illusion will be nearly the same, and the experiment, of course, be still more striking, when the motion is along a surface with which we are perfectly familiar, as a book which we hold in our hand, or a desk at which we are accustomed to sit.

I must request you, not to take for granted the result which I have now stated, but to repeat for yourselves an experiment, which it is so very easy to make, and which, I cannot but think is so very important, as to the influence of mere difference of time, in our estimation of longitudinal extent. It is an experiment, tried, unquestionably, in most unfavourable circumstances, when our tactual feelings, representative of extension, are so strongly fixed, by the long experience of our life; and yet, even now, you will find, on moving your hand, slowly and rapidly, along the same extent of surface, though with precisely the same degree of pressure in both cases, that it is as difficult to conceive the extent, thus slowly and rapidly traversed, to be the same, as it is difficult to conceive the extent of visual distance to be exactly the same, when you look alternately through the different ends of an inverted telescope. If when all other circumstances are the same, the different visual feelings, arising from difference of the mere direction of light, be representative of length, in the one case,—the longer or shorter succession of time, when all other circumstances are the same, has surely as much reason to be considered as representative of it, in the other case.

Are we, then, to believe, that the feeling of extension, or, in other words, of the definite figure of bodies, is a simple feeling of touch, immediate, original, and independent of time; or is there not rather reason to think, as I have endeavoured to show, that it is a compound feeling, of which time, that is to say, our notion of succession, is an original element?

[LECTURE XXV.]

ON THE DISTINCTION BETWEEN SENSATION AND PERCEPTION,—AND BETWEEN THE PRIMARY AND SECONDARY QUALITIES OF MATTER.

My last Lecture, Gentlemen, was chiefly employed in considering the nature of that complex process which takes place in the mind, when we ascribe the various classes of our sensations to their various external objects,—to the analysis of which process we were led, by the importance which Dr Reid has attached to the distinction of sensation and perception;—a sensation, as understood by him, being the simple feeling that immediately follows the action of an external body on any of our organs of sense, considered merely as a feeling of the mind; the corresponding perception being a reference of this feeling to the external body as its cause.

The distinction I allowed to be a convenient one, if the nature of the complex process which it expresses be rightly understood. The only question that seemed, philosophically, of importance, with respect to it, was, whether the perception in this sense,—the reference of the sensation to its external corporeal cause,—imply, as Dr Reid contends, a peculiar mental power, coextensive with sensation, to be distinguished by a peculiar name in the catalogue of our faculties, or be not merely one of the results of a more general power, which is afterwards to be considered by us,—the power of association,—by which one feeling suggests, or induces, other feelings that have formerly coexisted with it.

It would be needless to recapitulate the argument minutely, in its relation to all the senses. That of smell, which Dr Reid has himself chosen as an example, will be sufficient for our retrospect.

Certain particles of odorous matter act on my nostrils,—a peculiar sensation of fragrance arises,—I refer this sensation to a rose. This reference, which is unquestionably something superadded to the original sensation itself, is what Dr Reid terms the perception of the fragrant body. But what is the reference itself, and to what source is it to be ascribed? That we should have supposed our sensations to have had a cause of some sort, as we suppose a cause of all our feelings internal as well as external, may indeed be admitted. But if I had had no other sense than that of smell,—if I had never seen a rose,—or, rather, since the knowledge which vision affords is chiefly of a secondary kind, if I had no mode of becoming acquainted with the compound of extension and resistance, which the mere sensations of smell, it is evident, are incapable of affording,—could I have made this reference of my sensation to a quality of a fragrant body? Could I, in short, have had more than the mere sensation itself, with that general belief of a cause of some sort, which is not confined to our sensations, but is common to them with all our other feelings?

By mere smell, as it appears to me, I could not have become acquainted with the existence of corporeal substances,—in the sense in which we now understand the term corporeal,—nor, consequently, with the qualities of corporeal substances; and, if so, how could I have had that perception of which Dr Reid speaks,—that reference to a fragrant body, of which, as a body, I was before in absolute ignorance? I should, indeed, have ascribed the sensation to some cause or antecedent, like every other feeling; but I could as little have ascribed it to a bodily cause, as any feeling of joy or sorrow. I refer it now to a rose; because, being endowed with other sensitive capacities, I have previously learned, from another source, the existence of causes without, extended and resisting,—because I have previously touched or seen a rose, when the sensation of fragrance coexisted with my visual or tactual sensation; and all which distinguishes the perception from the mere sensation, is this suggestion of former experience, which reminds me now of other feelings, with the continuance or cessation of which, in innumerable former instances, the fragrance itself also continued or ceased. The perception in short, in smell, taste, hearing, is a sensation suggesting, by association, the notion of some extended and resisting substance, fragrant, vapid, vibratory,—a notion which smell alone, taste alone, hearing alone, never could have afforded; but which, when once received from any other source, may be suggested by these as readily as any other associate feeling that has frequently coexisted with them. To the simple primary sensations of vision the same remark may be applied. A mere sensation of colour could not have made me acquainted with the existence of bodies, that would resist my effort to grasp them. It is only in one sense, therefore,—that which affords us the knowledge of resistance,—that any thing like original perception can be found; and even in this, the process of perception, as I formerly explained to you, implies no peculiar power, but only common sensations, with associations and inferences of precisely the same kind, as those which are continually taking place in all our reasonings and trains of thought.

Extension and resistance, I need scarcely repeat, are the complex elements of what we term matter; and nothing is matter to our conception, or a body, to use the simpler synonymous term, which does not involve these elements. If we had no other sense than that of smell, and, therefore, could not have referred the sensations to any fragrant body, what, in Dr Reid's meaning of this term, would the supposed power of perception, in these circumstances, have been? What would it have been, in like manner, if we had had only the sense of taste in sweetness and bitterness,—or of hearing in melody,—or of vision in colour,—without the capacity of knowing light as a material substance, or the bodies that vibrated, or the bodies of another kind that were sweet or bitter? It is only by the sense of touch, or, at least, by that class of perceptions which Dr Reid ascribes to touch,—and which, therefore, though traced by us, in part, to another source, I, for brevity's sake, comprehend under that term in our present discussion,—it is only by touch that we become acquainted with those elements which are essential to our very notion of a body; and to touch, therefore, in his own view of it, we must be indebted, directly or indirectly, as often as we refer the sensations of any other class to a corporeal cause. Even in the supposed perceptions of touch itself, however, as we have seen, the reference of our feelings to an external cause is not demonstrative of any peculiar power of the mind, to be classed separately from its other faculties. But when a body is first grasped, in infancy, by fingers that have been accustomed to contract without being impeded, we learn to consider the sensation as the result of a cause that is different from our own mind, because it breaks an accustomed series of feelings, in which all the antecedents, felt by us at the time, were such as were before uniformly followed by a different consequent, and were expected, therefore, to have again their usual consequent. The cause of the new sensation, which is thus believed to be something different from our sentient self, is regarded by us as something which has parts, and which resists our effort, that is to say, as an external body;—because the muscular feeling, excited by the object grasped is, in the first place, the very feeling of that which we term resistance; and, secondly, because, by uniformly supplying the place of a definite portion of a progressive series of feelings, it becomes ultimately representative of that particular length of series, or number of parts, of which it thus uniformly supplies the place. Perception, then, even in that class of feelings by which we learn to consider ourselves as surrounded by substances extended and resisting, is only another name, as I have said, for the result of certain associations and inferences that flow from other more general principles of the mind; and with respect to all our other sensations, it is only another name for the suggestion of these very perceptions of touch, or at least of the feelings, tactual and muscular, which are, by Dr Reid, ascribed to that single sense. If we had been unsusceptible of these tactual and muscular feelings, and, consequently, had never conceived the existence of any thing extended and resisting till the sensation of fragrance, colour, sweetness, or sound had arisen, we should, after any one or all of these sensations, have still known as little of bodies without, as if no sensation whatever had been excited.

The distinction, then, on which Dr Reid has founded so much, involves, in his view of it, and in the view that is generally taken of it, a false conception of the nature of the process which he describes. The two words sensation and perception, are, indeed, as I have already remarked, very convenient for expressing, in one case, the mere existence of an external feeling,—in the other case, the reference which the percipient mind has made of this feeling to an external cause. But this reference is all, which the perception superadds to the sensation;—and the source of the reference itself we are still left to seek, in the other principles of our intellectual nature. We have no need, however, to invent a peculiar power of the mind for producing it; since there are other principles of our nature, from which it may readily be supposed to flow,—the principle by which we are led to believe, that every new consequent, in a train of changes, must have had a new antecedent of some sort in the train,—and the principle of association, by which feelings, that have usually coexisted, suggest or become representative of each other. With these principles, it certainly is not wonderful, that when the fragrance of a rose has uniformly affected our sense of smell, as often as the flower itself was presented to us, we should ascribe the fragrance to the flower which we have seen and handled;—but though it would not be wonderful, that we should make it, it would indeed be wonderful, if, with these principles, we did not make that very reference, for which Dr Reid thinks it necessary to have recourse to a peculiar faculty of perception.

Such, then, is the view, which I would take of that distinction of sensation and perception, which Dr Reid, and the philosophers who have followed him, and many of philosophers, too, that preceded him,—for the distinction, as I have said, is far from being an original one,—have understood in a different sense; in consequence, as I cannot but think, of a defective analysis of the mental process, which constitutes the reference of our feelings of this class to causes that are without.

There is another distinction, which he has adopted from the philosophers that preceded him, and which forms an important part of his system of perception,—a distinction, that is just to a certain extent,—though not to the full extent, and in the precise manner, in which he and other writers have maintained;—and with respect to which, therefore, it will be necessary to point out to you, how far I conceive it to be safely admissible. I allude to the division, which has been formed of the primary and secondary qualities of matter.

“Every one knows that extension, divisibility, figure, motion, solidity, hardness, softness, and fluidity, were by Mr Locke called primary qualities of body; and that sound, colour, taste, smell, and heat or cold, were called secondary qualities. Is there a just foundation for this distinction? Is there any thing common to the primary, which belongs not to the secondary? And what is it?

“I answer, that there appears to me to be a real foundation for the distinction; and it is this: That our senses give us a direct and a distinct notion of the primary qualities, and inform us what they are in themselves; but of the secondary qualities, our senses give us only a relative and obscure notion. They inform us only, that they are qualities that affect us in a certain manner, that is, produce in us a certain sensation; but as to what they are in themselves, our senses leave us in the dark.

“The notion we have of primary qualities is direct, and not relative only. A relative notion of the thing, is, strictly speaking, no notion of the thing at all, but only of some relation which it bears to something else.

“Thus gravity sometimes signifies the tendency of bodies towards the earth; sometimes it signifies the cause of that tendency: When it means the first, I have a direct and distinct notion of gravity: I see it, and feel it, and know perfectly what it is; but this tendency must have a cause: We give the same name to the cause; and that cause has been an object of thought and of speculation. Now what notion have we of this cause, when we think and reason about it? It is evident, we think of it as an unknown cause, of a known effect. This is a relative notion, and it must be obscure; because it gives us no conception of what the thing is, but of what relation it bears to something else. Every relation which a thing unknown bears to something that is known, may give a relative notion of it; and there are many objects of thought, and of discourse, of which our faculties can give no better than a relative notion.

“Having premised these things to explain what is meant by a relative notion, it is evident, that our notion of primary qualities is not of this kind; we know what they are, and not barely what relation they bear to something else.

“It is otherwise with secondary qualities. If you ask me, what is that quality or modification in a rose which I call its smell, I am at a loss to answer directly. Upon reflection I find, that I have a distinct notion of the sensation which it produces in my mind. But there can be nothing like to this sensation in the rose, because it is insentient. The quality in the rose is something which occasions the sensations in me; but what that something is, I know not. My senses give me no information upon this point. The only notion, therefore, my senses give is this, That smell in the rose is an unknown quality or modification, which is the cause or occasion of a sensation which I know well. The relation which this unknown quality bears to the sensation with which nature hath connected it, is all I learn from the sense of smelling; but this is evidently a relative notion. The same reasoning will apply to every secondary quality.

“Thus I think it appears, that there is a real foundation for the distinction of primary from secondary qualities; and that they are distinguished by this, that of the primary we have by our senses a direct and distinct notion; but of the secondary only a relative notion, which must, because it is only relative, be obscure; they are conceived only as the unknown causes or occasions of certain sensations with which we are well acquainted.”[92]

Though, as I have explained to you fully, in my former Lectures, we should not,—at least in far the greater number of our sensations,—have considered them, originally, as proceeding from external causes, we yet, after the acquisitions of knowledge, with which the first years of our life enrich us, believe, that there is an external cause of all our sensations,—of smells and tastes, as much as of those feelings of the mind, which constitute our notions of extension and resistance. But the difference, in these cases, is, that though we learn, by experience of certain successions or co-existences of feelings, to refer to a corporeal cause our sensations of fragrance, and various other species of sensations, there is nothing in the sensation of fragrance itself, or in the other analogous sensations, of which I speak, that might not indicate as much a cause directly spiritual, as a cause like that to which we at present give the name of body,—while the very notion of extension and resistance combined, seems necessarily to indicate a material cause, or rather is truly that which constitutes our very notion of matter.

We believe, indeed, that our sensations of fragrance, sweetness, sound, have causes of some sort, as truly as we believe, that our feelings of extension and resistance have a cause, or causes of some sort; but if we have previously given the name of matter, with direct reference to the one set of effects, and not with direct reference to the other, it necessarily follows, that, in relation to matter, as often as we speak or think of it, the qualities which correspond with the one set of effects, that have led us to use that name, must be regarded by us as primary, and the others, which may, or may not coexist with these, only as secondary. An external body may, or may not be fragrant, because fragrance is not one of the qualities previously included by us in our definition of a body; but it must be extended, and present an obstacle to our compressing force, because these are the very qualities, which we have included in our definition, and without which, therefore, the definition must cease to be applicable to the thing defined.

If, originally, we had invented the word matter to denote the cause, whatever it might be, of our sensations of smell, it is very evident, that fragrance would then have been to us the primary quality of matter, as being that which was essential to our definition of matter,—and all other qualities, by which the cause of smell might, or might not at the same time affect our other senses, would then have been secondary qualities only,—as being qualities compatible with our definition of matter, but not essential to it.

What we now term matter, however, I have repeatedly observed,—is that which we consider as occupying space, and resisting our effort to compress it; and those qualities of matter may well be said to be primary, by which matter itself, as thus defined, becomes known to us,—or by the union of which, in our conception, we form the complex notion of matter, and give or withhold that name according as these qualities are present or absent. Extension and resistance are the distinguishing qualities that direct us in all our applications of the word which comprehends them. They are truly primary qualities, therefore; since, without our consideration of them, we never could have formed the complex notion of the substance itself, to which we afterwards, in our analysis of that complex notion, ascribe them separately as qualities;—and all the other qualities, which we may afterwards find occasion to refer to an extended resisting substance, must evidently be secondary, in reference to those qualities, without which as previously combined in our thought, we could not have had the primary notion of the substance to which we thus secondarily refer them. If, in the case which we have already frequently imagined, of the single sense of smell, we had been absolutely unsusceptible of every other external feeling, we might, indeed, have considered our sensation as the effect of some cause,—and even of a cause that was different from our mind itself; but it is very evident that we could not have considered it as the effect of the presence of matter, at least as that term is now understood by us. If, in these circumstances,—after frequent repetition of the fragrance, as the only quality of bodies with which we could be acquainted,—we were to acquire in an instant all the other senses which we now possess,—so as to become capable of forming that complex notion of things extended and resisting, which is our present notion of matter, we should then, indeed, have a fuller notion of the rose, of the mere fragrance of which we before were sensible, without knowing of what it was the fragrance, and might learn to refer the fragrance to the rose, by the same coexistences of sensations which have led us, in our present circumstances, to combine the fragrance with other qualities, in the complex conception of the flower. Even then, however, though the fragrance, which was our first sensation, had truly been known to us before the other qualities, and though the sensation, therefore, would deserve the name of primary, the reference of this earlier feeling to the external rose as its cause, would still truly be secondary to the earlier reference, or rather to the earlier combination of other qualities, in one complex whole, by which we had formed to ourselves the notion of the extended and resisting rose, as a body, that admitted the subsequent reference of the delightful sensation of fragrance to be made to it, as the equal cause of these different effects.

In this sense, then, the distinction of the primary and secondary qualities of matter is just,—that, whatever qualities we refer to a material cause must be, in reference, secondary to those qualities that are essential to our very notion of the body, to which the subsequent reference of the other qualities is made. We have formed our definition of matter; and, as in every other definition of every sort, the qualities included in the definition, must always, in comparison of other qualities, be primary and essential, relatively to the thing defined.

Nor is this all.—It will be admitted likewise, that the qualities termed primary,—which alone are included in our general definitions of matter, and which are all, as we have seen, modifications of mere extension and resistance, are, even after we have learned to consider the causes of all our sensations as substances external to the mind, still felt by us to be external, with more clearness and vividness, than the other qualities, which we term secondary. The difference is partly, and chiefly, in the nature of the sensations themselves, as already explained to you, but depends also, I conceive, in no inconsiderable degree, on the permanence and universality of the objects which possess the primary qualities, and the readiness with which we can renew our feeling of them at will, from the constant presence of our own bodily frame, itself extended and resisting, and of the other causes of these feelings of extension and resistance, that seem to be every where surrounding us. Tastes, smells, sounds,—even colours though more lasting than these—are not always before us;—but there is not a moment at which we cannot, by the mere stretching of our hand, produce at pleasure, the feeling of something extended and resisting. It is a very natural effect of this difference, that the one set of causes which are always before us, should seem to us, therefore, peculiarly permanent, and the other set, that are only occasionally present, should seem almost as fugitive as our sensations themselves.

In these most important respects, there is, then, a just ground for the distinction of the primary from the secondary qualities of bodies. They are primary in the order of our definition of matter; and they are felt by us as peculiarly permanent, independently of our feelings, which they seem at every moment ready to awake. The power of affecting us with smell, taste, sight, or hearing, may or may not be present; but the power of exciting the feelings of extension and resistance is constantly present, and is regarded by us as essential to our very notion of matter,—or, in other words, we give the name of matter, only where this complex perception is excited in us. We seem, therefore, to be constantly surrounded with a material world of substances extended and resisting, that is to say, a world of substances capable of exciting in us the feelings which are ascribed to the primary quality of matter;—but still the feeling of these primary qualities, which we regard as permanent, is not less than the feeling of the secondary qualities, a state or affection of the mind, and nothing more;—and in the one case, as much as in the other, in the perception of the qualities termed secondary, as much as of the qualities termed primary, the feeling, when it occurs, is the direct or immediate result of the presence of the external body with the quality of which it corresponds;—or, if there be any difference in this respect, I conceive that our feeling of fragrance, or sweetness, was, originally at least, a more immediate result of the presence of odorous or sapid particles,—than any feeling of extension, without the mind, was the effect of the first body which we touched.

To the extent which I have now stated, then, the difference of these classes of qualities may be admitted. But as to the other differences asserted, they seem to be founded on a false view of the nature of perception. I cannot discover any thing in the sensations themselves, corresponding with the primary and secondary qualities, which is direct, as Dr Reid says, in the one case, and only relative in the other. All are relative, in his sense of the term, and equally relative,—our perception of extension and resistance, as much as our perception of fragrance or bitterness. Our feeling of extension is not itself matter, but a feeling excited by matter. We ascribe, indeed, our sensations as effects to external objects that excite them; but it is only by the medium of our sensations that these, in any case, become known to us as objects. To say that our perception of extension is not relative, to a certain external cause of this perception, direct or indirect, as our perception of fragrance is relative to a certain external cause, would be to say that our perception of extension, induced by the presence of an external cause, is not a mental phenomenon, as much as the perception of fragrance, but is something more than a state of the mind; for, if the perception of extension be, as all our perceptions and other feelings must surely be, a mental phenomenon, a state of mind, not of matter, the reference made of this to an external cause, must be only to something which is conceived relatively as the cause of this feeling. What matter is independently of our perception, we know not, and cannot know, for it is only by our sensations that we can have any connexion with it; and even though we were supposed to have our connexion with it enlarged, by various senses additional to those which we possess at present, and our acquaintance with it, therefore, to be far more minute, this very knowledge, however widely augmented, must itself be a mental phenomenon, in like manner, the reference of which, to matter, as an external cause, would still be relative only like our present knowledge. That the connexion of the feeling of extension, with a corporeal substance really existing without, depends on the arbitrary arrangement made by the Deity; and that all of which we are conscious might, therefore, have existed, as at present, though no external cause had been, Dr Reid, who ascribes to an intuitive principle, our belief of an external universe, virtually allows; and this very admission surely implies, that the notion does not, directly and necessarily, involve the existence of any particular cause, whatever it may be in itself, by which the Deity has thought proper to produce the corresponding feeling of our mind. It is quite evident, that we cannot, in this case, appeal to experience, to inform us what sensations or perceptions are more or less direct; for experience, strictly understood, does not extend beyond the feelings of our own mind, unless in this very relative belief itself, that there are certain external causes of our feelings,—causes which it is impossible for us not to conceive as really existing, but of which we know nothing more than that our feelings, in all that wide variety of states of mind, which we express briefly by the terms sensation or perception, are made to depend on them. In the series of states in which the mind has existed, from the first moment of our life, to the present hour, the feelings of extension, resistance, joy, sorrow, fragrance, colour, hope, fear, heat, cold, admiration, resentment, have often had place; and some of these feelings, it has been impossible for us not to ascribe to a direct external cause; but there have not been in the mental series, which is all of which we can be conscious, both that feeling of the mind which we term the perception of extension, and also body itself, as the cause of this feeling; for body, as an actual substance, cannot be a part of the consciousness of the mind, which is a different substance. It is sufficient for us to believe, that there are external causes of this feeling of the mind, permanent and independent of it, which produce in regular series, all those phenomena that are found by us in the physical events of the universe, and with the continuance of which, therefore, our perceptions also will continue; we cannot truly suppose more, without conceiving our very notion of extension, a mental state, to be itself a body extended, which we have as little reason to suppose, as that our sensation of fragrance, another mental state, is itself a fragrant body. It is needless to prolong this discussion, by endeavouring to place the argument in new points of view. The simple answer to the question, “Is our notion of extension, or of the other primary qualities of matter, a phenomenon or affection of matter or of mind?” would be of itself sufficient; for if it be a state of the mind, as much as our feeling of heat or of fragrance, and a state produced by the presence of an external cause, as our sensations of heat or fragrance are produced, then there is no reason to suppose, that the knowledge is, in one case, more direct than in the other. In both, it is the effect of the presence of an external cause, and in both it must be relative only,—to adopt Dr Reid's phrase,—to that particular cause which produced it; the knowledge of which cause, in the case of extension, as much as in the case of fragrance, is nothing more than the knowledge, that there is without us, something which is not our mind itself, but which exists, as we cannot but believe, permanently and independently of our mind, and produces according to its own varieties, in relation to our corporeal frame at one time, that affection of the mind which we denominate the perception of extension; at another time, that different affection of the mind, which we denominate the perception of fragrance. What it is, as it exists in absolute independence of our perceptions, we who become acquainted with it, only by those very perceptions, know not, in either case; but we know it at least,—which is the only knowledge important for us,—as it exists relatively to us; that is to say, it is impossible for us, from the very constitution of our nature, not to regard the variety of our perceptions, as occasioned by a corresponding variety of causes, external to our mind; though, even in making this reference, we must still believe our perceptions themselves, to be altogether different and distinct from the external causes, whatever they may be, which have produced them; to be, in short, phenomena purely mental, and to be this equally, whether they relate to the primary or the secondary qualities of matter; our notion of extension, in whatever way the Deity may have connected it with the presence of external things, being as much a state of the mind itself, as our notion of sweetness or sound.

These observations, on the process of suggestion, which, in the reference to an external cause, distinguishes our perceptions from our simpler sensations,—and on the real and supposed differences of the primary and secondary qualities of matter,—will have prepared you, I trust, for understanding better the claim which Dr Reid has made to the honour of overthrowing what he has termed the ideal system of perception. It is a claim, as I have said, which appears to me truly wonderful, both as made by him and admitted by others; the mighty achievement which appeared to him to be the overthrow of a great system, being nothing more, than the proof that certain phrases are metaphorical, which were intended by their authors to be understood only as metaphors.

In perception there is, as I have already frequently repeated, a certain series—the presence of an external object—the affection of the sensorial organ—the affection of the sentient mind. As the two last, however, belong to one being—the being called self—which continues the same, while the external objects around are incessantly changing;—it is not wonderful, that, in speaking of perception, we should often think merely of the object as one, and of ourself, (this compound of mind and matter,) as also one,—uniting the organic and mental changes, in the single word which expresses our perception. To see and to hear, for example, are single words, expressive of this whole process—the bodily as well as the mental part—for we do not consider the terms as applicable, in strict philosophic propriety, to cases, in which the mere mental affection is the same, but the corporeal part is believed by us to be different,—as in sleep, or reverie, when the castle, the forest, the stream, rise before us as in reality, and we feel as if we were truly listening to voices which we love. That we feel, as if we were listening, and feel as if we saw, is our language, when, in our waking hours, we speak of this phenomena of our dreams,—not that we actually saw and heard—thus evidently shewing, that we comprehend, in these terms,—when used without the qualifying words as if—not the mental changes of state only, but the whole process of perception, corporeal as well as mental. The mere organic part of the process, however, being of importance, only as it is followed by the mental part,—and being always followed by the mental part,—scarcely enters into our conception, unless in cases of this sort, when we distinguish perception from vivid imagination, or when the whole compound process of perception is a subject of our philosophic inquiry. As sight, hearing, perception, involve, in a single word,—process both mental and corporeal,—so, I have no doubt, that idea, though now confined more strictly to the feelings of the mind, was long employed with a more vague signification, so as sometimes to mean the mental affection, sometimes the organic affection, sometimes both;—in the same manner, as at present we speak of sight, sometimes as mental, sometimes as organic, sometimes as both. It comprehends both, when we distinguish the mountain or forest which we see, from the mountain or forest of which we dream. It is mental only, when we speak of the pleasure of sight. It is organic only, when we say of an eye, in which the passage of the rays of light has become obstructed, that its sight is lost, or has been injured by disease.

The consideration of this double sense of the term idea, in some of the older metaphysical writers, corresponding with our present double sense of the word perception, as involving both the corporeal and mental part of the process, removes, I think, much of that apparent confusion, which is sometimes to be found in their language on the subject; when they combine with the term expressions, which can be understood only in a material sense, after combining with it, at other times, expressions, which can be understood only of the mind; as it is not impossible that a period may arrive, when much of our reasoning, that involves no obscurity at present, may seem obscure and confused, to our successors, in that career of inquiry, which, perhaps, is yet scarcely begun; merely because they may have limited, with stricter propriety, to one part of a process, terms, which we now use as significant of a whole process. In the same manner, as we now exclude wholly from the term idea every thing organic, so may every thing organic hereafter be excluded from the term sight; and from the simple phrase, so familiar at present, that an eye has lost its sight, some future philosopher may be inclined to assert, that we, who now use that phrase, consider the perception of vision, as in the material organ; and, if he have the talents of Dr Reid, he may even form a series of admirable ratiocinations, in disproof of an opinion which nobody holds, and may consider himself, and perhaps, too, if he be as fortunate as the author of the Inquiry into the Human Mind, may be considered, by others, as the overthrower of a mighty system of metaphysical illusion.

How truly this has been the case, in the supposed overthrow of the ideal system, I shall proceed to shew in my next Lecture.