sensorial particles,-if the affection of a long line of these particles be necessary, on the presence of a particular object, is not more improbable in itself, than this instant and universal influence of gravitation, that varies with all the varying positions of a distant object.

But is it, indeed, certain, that, in sensation, there is an affection of the central brain, whether immediate or progressive? Is it not possible, at least, or more than possible, that the state of the mind, when we perceive colours and sounds, may be the immediate consequent of the altered state of that part of the sensorial organ, which forms the expansion of the nerve in the eye or ear? The sensations must be supposed, in every theory, to be the consequents of states induced in some sensorial particles, and there is nothing but the mere names of brain and nerve, invented by ourselves, and the notions which we have chosen, without evidence, to attach to these mere names, which would mark the sensorial particles in the nervous expanse itself, as less fitted to be the immediate antecedents of sight and hearing, than the similar sensorial particles in any portion of the central mass of the brain. There is no reason, in short, a priori, for supposing that a state of the sensorial particles of the nerves cannot be the cause of sensation, and that the sensation must be the effect of a state equally unknown, of apparently similar particles, in that other part of the general sensorial organ, which we have denominated the brain. Sensation, indeed, is prevented by decay, or general disease of the brain, or by separation of the nerve, or pressure on it, in any part of its course, But it is far from improbable, that these causes, which must evidently be injurious to the organ, may act, merely by preventing that sound state of the nerve which is necessary for sensation, and which, in an organ so very delicate, may be affected by the slightest influences,-by influences far slighter than may naturally be expected to result from such an injury of such a part. The nerves and brain, together, form one great organ; and a sound state of the whole organ, even from the analogy of other grosser organs, may well be supposed to be necessary for the healthy state and perfect function of each separate part.

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 shows 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 froin the chain. Í 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 the body."*

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

* On the Intellectual Powers, Essay II. chap. ii.

The horse as wanton, and almost as fleet,

That skims the spacious meadow at full speed,

Then stops, and snorts, and, throwing high his heels,
Starts to the voluntary race again;

The very kine, that gambol at high noon,—
The total herd,-receiving first from one,
That leads the dance, a summons to be gay;
Though wild their strange vagaries, and uncouth
Their efforts, yet resolved, with one consent,
To give such act and utterance as they may
To ecstasy, too big to be suppressed."**

It is this appearance of happy life which spreads a charm over every little group, with which Nature animates her scenery; and he who can look without interest on the young lamb, as it frolics around the bush, may gaze, indeed, on the magnificent landscape as it opens before him,-but it will be with an eye which looks languidly, and in vain, for pleasure which it cannot find.

These observations, on our muscular pains and pleasures, in conformity with that view of them which I endeavoured to give you, in a former lecture, are not digressive now, nor uselessly repeated. It is of great importance for the applications which we have to make, that you should be fully aware that our muscular frame is not merely a part of the living machinery of motion, but is also truly an organ of sense. When I move my arm, without resistance, I am conscious of a certain feeling; when the motion is impeded, by the presence of an external body, I am conscious of a different feeling, arising partly, indeed, from the mere sense of touch, in the moving limb compressed, but not consisting merely in this compression, since, when the same pressure is made by a foreign force, without any muscular effort on my part, my general feeling is very different. It is the feeling of this resistance to our progressive effort, (combined, perhaps, with the mere tactual feeling) which forms what we term our feeling of solidity or hardness; and, without it, the tactual feeling would be nothing more than a sensation indifferent or agreeable, or disagreeable or severely painful, according to the force of the pressure, in the particular case; in the same way, as the matter of heat, acting, in different degrees, on this very organ of touch, and on different portions of its surface, at different times, produces all the intermediate sensations, agreeable, disagreeable, or indifferent, from the pain of excessive cold, to the pain of burning; and produces them in like manner, without suggesting the presence of any solid body, external to ourselves.

Were the cube, therefore, in the case supposed, pressed, for the first time, on the hand, it would excite a certain sensation, indeed, but not that of resistance, which always implies a muscular effort that is resisted, and consequently not that of hardness, which is a mode of resistance. It would be very different, however, if we fairly made the attempt to press against it; for, then, our effort would be impeded, and the consequent feeling of resistance would arise; which, as co-existing in this case, and in every case of effort, with the particular sensation of touch, might afterwards be suggested by it, on the simple recurrence of the same sensation of touch, so as to excite the notion of hardness, in the body touched, without the renewal of any muscular effort on our part, in the same manner as the angular surfaces of the cube, if we chance to turn our eye on it, are suggested by the mere plane of colour, which it presents to our immediate vision, and which is all that our imme* Cowper's Task, Book IV.

diate vision would, of itself, have made known to us. The feeling of resistance, then, I trust, it will be admitted, and consequently of hardness, and all the other modes of resistance, is a muscular, not a tactual feeling.

But though the resistance or hardness of the cube, as implying the experience of some counter effort, may not be immediately sensible to our superficial organ of touch, are not its dimensions so perceived? Its cubical form, indeed, it will be allowed, cannot be felt, since only one of its surfaces is supposed to be pressed upon the hand; but, is not at least this square surface perceived immediately? In short, does not touch, originally and immediately, convey to us the knowledge of extension?

With our present complete belief of external things, indeed, and especially of our organs of sense, the most important of these, the origin of our knowledge of extension, seems to us a matter of very easy explanation. The square surface presses on our organ of touch,-it affects not a single physical point merely, but a portion of the organ, corresponding exactly, in surface, with itself; and the perception of the similar square, it will be said, thus immediately arises. But, in all this easy explanation, it is very strangely forgotten, that the feeling, whatever it may be, which the impression of the square surfaces produces, is not itself the square configuration of our tactual organ, corresponding with that surface, but the state of a very different substance, which is as little square, as it is round or elliptical,-which is, indeed, from its own absolute simplicity, incapable of resemblance in shape to any thing; and the resemblance of which, therefore, to the shape of the mere organ, is as little to be expected in the sensations of touch,-as that other state of mind, which constitutes the sensation of the fragrance of a rose, can be expected to resemble the shape of the odorous particles themselves, or of the organ of smell, which is affected by them. The very knowledge which touch is supposed to give, is, in this case, most inconsistently assumed, as existing in the mind, before the very touch which is supposed to give it. If, indeed, the mind could know, that a part of its external corporeal organ is compressed into the form of a square, or that another square surface is compressing that organ, the difficulty would be at an end; for it would then, most undoubtedly, have that very knowledge of extension, the origin of which we seek. But it is not explained, how the mind, which alone can have sensation or knowledge, and which certainly is not square itself, is to be made acquainted with the squareness of its own corporeal organ, or of the foreign body; nor, indeed, how the squareness of the mere external organ should produce this particular affection of the mind, more than if the organ were compressed into the shape of a polygon of one thousand sides.

Let it be supposed, that, when a small cube is pressed on the hand, one hundred physical points of the organ of touch are affected in a certain manner. We have, it is said, an immediate perception of a square surface. Let it next be supposed, that, instead of one hundred of these continuous points of the organ, an equal number of points, at various distances in the surface of the body, are affected in the same manner. On this supposition it will scarcely be said, that the perception of a square would arise, when there is no square, more than any other imaginable form, in the space comprehended in the pressure. Yet what difference is there, in these two cases, to a mind that is, by supposition, absolutely ignorant of every bodily organ, and consequently alike ignorant of the nearness or distance of the points of the organ of touch? In both cases, one hundred points, equally sensible, are affected,

and are affected precisely in the same manner;-and there is truly no difference, unless we tacitly suppose the mind to be conscious of the bodily frame, and, therefore, of the continuity of certain points of the organ of touch, with the other points that are proximate to them,-a sort of knowledge, for which it would not be easy to account, and which it is impossible to conceive, without conceding the very point in question. A little attentive reflection on the circumstances of these two cases, will, perhaps, aid you in freeing your minds from the illusive belief, of which it may not be easy for you at first to divest yourselves,-that the continuity and similarity of shape, which are known to us the inquirers, are known also to that little sentient being, whose first elements of knowledge we are endeavouring to trace.

We are too apt to forget, in inquiries of this sort, that it is not in our organ of touch merely, that a certain extent of the nervous extremity of our sensorial organ is affected. This occurs, equally, in every other organ. In the superficial expansion of the nerves of hearing, smell, taste, for example, it is not a point merely that is affected, but a number of continuous points, precisely, as in the superficial organ of touch; and if, therefore, the notion of extension in general, or of figure, which is limited extension, arose whenever a part of the nervous expansion was affected in any way, we should derive these notions as much from a taste, or a smell, or a sound, as from any of the configurations or affections of our organ of touch.

It is not, therefore, merely because a certain limited part of the sensorial organ is affected, that we have the notion of the square surface, in the case supposed by us for, if this alone were necessary, we should have square inches, and half inches, and various other forms, rectilinear or curvilinear, of fragrance and sound.

But, it may perhaps be urged, though all our organs must, indeed, exist equally with our organ of touch of a certain shape when affected,—and though the sensorial figure of our other organs is not accompanied with any of those mental affections, which constitute the perception of angular or curvilinear figure, there is something in the nature of that part of the sensorial organ, which terminates on the general surface of the body, that impresses the mind, immediately, with a sensation, corresponding with the exact figure, in which the organ may itself exist. When the square, therefore, in the case imagined by us, is impressed upon the organ, the mental affection which constitutes our notion of a square may immediately arise, though it would not arise from the similar squareness of our organs of smell or hearing.

In answer to this mere supposition, I may remark, that the sensorial organ of touch exists, at every moment, of a certain shape, and that we yet have no perception of this shape, so as to be able to delineate the whole extent of our tactual organ, in the same manner as we could delineate the impressing square, in the case supposed: or, if it be said, that the configuration of the organ does not excite this mental affection, in the quiescent state of the part, but only when it is itself affected, I may remark, that we are as little able to delineate its figure when we are exposed to the action of heat, which yet acts most powerfully upon this very organ, inducing sensations, at least as vivid as those of hardness or figure.

It may still, however, be contended, for in a question of this sort I wish fairly to imagine every possible argument-it may still be contended, that, though the organ of touch has no effect in this way, merely as configured, and might, in any other configuration, operate precisely in the same manner