may lose the power of giving pain, it would be difficult to say; and how far the gradual alleviation of such pains as toothache, rheumatism, wounds, fractures, dislocations, even cancers, and the power of bearing these maladies with equanimity, may be due to this merciful provision in our constitution, deserves the consideration of pathologists.

Another cause which contributes to the diminishing and gradual cessation of the pain or pleasure of longcontinued sensations, is that they lose their novelty, and so lose that power of fixing the attention upon themselves. We have said that one cause of any sensation drawing the attention exclusively to itself was its novelty; but if any, either pleasant or painful, sensation, be long continued, it of course loses that power over the attention, and the mind becomes more at liberty to attend to other objects. This, doubtless, is one of the reasons why the pain and the pleasure of any sensation is always greatest on first experiencing it. The very novelty of it draws the attention forcibly to it; but when the novelty passes away, other sensations acquire power to draw away the attention from it: hence the efficacy of new sights and sounds employed by nurses to draw off the attention of children from causes of pain and irritation. We shall have occasion to return to this important phenomenon in treating of memory.

We add for the present, respecting this abatement of the pleasure or pain entering as elements into our sensations on the prolongation or repetition of them, that it is the cause of so large a proportion of our ordinary sensations being indifferent; and not that any of them were from the first indifferent.

Those sensations which gave more exquisite delight on first experiencing them, seem to pursue a rather different course when frequently repeated. They, too, first become indifferent by repetition; but on the repetition continuing, they become unpleasant and irksome, till

the unpleasantness or irksomeness itself follows the general law, and sinks into indifference. A savoury dish presented for many days successively, becomes nauseous; but if it continue to be repeated, especially if it be the only means provided of allaying hunger, the dislike with which it was received passes away. A piece of music that threw us into ecstasy when we first heard it, becomes, by long-continued repetition, first indif ferent, then irksome, and again indifferent. These more exquisitely pleasant sensations proceed by a more circuitous route than ordinary sensations to the common tomb of indifference. A sensation, or series of sensations, that have thus lost their power of yielding pleasure, and have become indifferent, may even recover the power of yielding pleasure, but pleasure of a different kind. It may become connected in the mind with other pleasing sensations, and yield pleasure by recalling these. A tune that has ceased to give pleasure from its own original power, may, by being sung on occasions of hilarity and social enjoyment, fill the heart with gladness when it is occasionally heard. The National Anthem, by being used as an expression of loyalty and nationality, may yield enjoyment by exciting feelings of respect and affection for a beloved sovereign in the hearts of a loyal people. The sound of bagpipes in a foreign land may excite overpowering delight in the heart of a Scottish Highlander, by recalling to him the scenes of his distant home.

Unpleasant sensations follow a similar course by repetition. They become first indifferent, many of them afterwards pleasant, and then again sink into indifference. Such substances as tobacco, mustard, porter, ardent spirits, occasion at first unpleasant sensations; on being repeated frequently, the organs of taste become reconciled to them, and they become indifferent; and they may afterwards recover a secondary power of yielding pleasure, chiefly that of allaying a painful sensation occasioned by

their absence for this, we apprehend, comes to be the only pleasure which the use of such substances as tobacco, mustard or alcoholic liquors, yields to those who are addicted to the use of them. The original dislike of them, and the pleasure which succeeded to it, have both long since ceased; but the continued use of them has created a craving after them by their action on the gastric or olfactory nerves, the pain of which they allay for a short time; and the allaying of pain is one of the most common, as it is the most exquisite, of our enjoyments. Some of these habits, particularly smoking tobacco and drinking intoxicating liquors, may derive their secondary power of yielding pleasure, from their recalling scenes of companionship and hilarity.

We come now to two observations on sensation of the very highest importance in the study of the human mind, and which will necessarily modify the form and order of our further investigations. The first observa

tion is

7. That none of these classes of sensations, nor all of them together, could of themselves convey to the mind any notion of any being external to the mind itself, and consequently could never awaken any of those emotions or operations of the mind which imply the knowledge of an external world or of other minds. This truth is now generally, perhaps we ought to say universally, admitted by all who desire to be regarded as mental philosophers in the proper sense of the word-men who seek their knowledge of the mind as they do their knowledge of the material world, by observing phenomena, and who do not feel themselves at liberty to indulge in the flights and fancies of what is called "transcendental philosophy" -a sort of philosophy which we are more disposed to compare to an ineffectual groping in mud, than to the more pleasant, though equally ineffectual, mental exercise of flights and fancies.

Without attempting to repeat, or to abridge, the various

arguments by which this great truth has been proved to the satisfaction of all mental philosophers, we shall endeavour to give such an illustration of it as may reconcile to it the minds of persons unaccustomed to mental investigations.

Let us, for this purpose, suppose a human mind, with all its natural faculties, connected with a body possessing all the organs of sense, but without power to move any muscle of the body. If we may be indulged in so monstrous a supposition, let us suppose a human mind connected with a human head laid motionless, with its face upwards, like a head of wax; the eye and the mouth open, but perfectly motionless, the nostrils and the ears exposed to odours and sounds, and the whole face having the sense of touch, and all the organs of sense perfectly fitted for conveying to the mind all intimations from without; and let us consider what operations the mind would be capable of in such circumstances, and the nature and amount of knowledge to which it might attain.

We have said, that in such circumstances it could never attain to any conception of anything external to itself, or of any being besides itself.

Let us commence with the sense of sight; for, if we succeed in convincing any one that this sense would not of itself convey the notion of external objects, we shall have no difficulty in convincing that none of the other senses would convey to it that notion. We are so accustomed to imagine that we see external objects by the eye and not mere varieties of light and shade, which we learn by practice to decipher, and to understand that these varieties of light and shade are produced by external objects in various positions-that persons unacquainted with metaphysical inquiries may find it difficult to believe that any object can be presented to the eye without conveying the idea of its existence external to the eye. It may help to get them over this difficulty to consider

how easily the eye is deceived by a well-executed painting. The painter, according to certain rules of perspective, draws an outline of different objects, in various positions and various distances; he then colours his outline with various tints, lighter and darker; and the result is that he makes people imagine that they see objects in different positions and different distances, when all that they do see are merely a few lines, and different patches of colour, on a perfectly flat surface. Again, if any person look attentively for some time at a bright object, as, for example, a window through which he sees a bright sky, and then shut his eyes, he will see the window, as if it were floating before him, of a different colour from what it was when his eyes were open looking at it; and yet he knows that it is not floating before him, but entirely in his own mind. These facts may aid then in believing what has been proved to the satisfaction of the most sceptical-partly by investigating the nature of visual sensations, and partly by observing phenomena that it is only by practice and experience that we learn from the sense of sight the existence, and positions, and comparative distances of external objects. In a celebrated case, reported by Dr. Cheselden, of a youth receiving the sense of sight by a surgical operation, it was found that, on first opening his eyes to the light, all objects, at whatever distances they might be, appeared to touch the eye. We apprehend that this notion of external objects touching the eye was derived, not from the sense of sight, but from his previous knowledge that there are external objects, and his habit of tracing all sensations to external objects. Had these been his first sensations, he probably would not have known that they came through the eye; but he was previously acquainted with the structure of his body, he was familiar with the sensations derived through the other organs of sense, he perceived at once that these new sensations were different from the others, that they