There is one emotion, in particular, that is capable of so many modifications, and has so extensive a sway over human life, which it may be said almost to occupy from the first wishes of our infancy to the last of our old age, that it cannot fail to be combined with many of our other feelings, both sensitive and intellectual. The emotion to which I allude is desire; a feeling which may exist of various species and degrees, from the strongest passion of which the mind is susceptible, to the slightest wish of knowing a little more accurately the most trifling object before us;—and though, in speaking of it at present, I am anticipating what, according to the strict division which we have made, should not be brought forward till we consider the emotions in general, this anticipation is absolutely unavoidable for understanding some of the most important phenomena, both of perception, which we have been considering, and of those intellectual faculties which we are soon to consider. I need not repeat to you, that Nature is not to be governed by the systems which we form; that though our systematic arrangements ought not to be complicated, her phenomena are almost always so; and that, while every thing is thus intermixed and connected with every thing in the actual phenomena of mind as well as of matter, it would be vain for us to think of accommodating our physical discussions with absolute exactness, even to the most perfect divisions and subdivisions which we may be capable of forming. All that is necessary is, that we should not depart from our order of arrangement without some advantage in view, and an advantage greater than the slight evil which may arise from the appearance of temporary confusion.
The reason of my anticipation, in the present instance, is to explain to you what I conceive to constitute the phenomena of attention,—a state of mind which has been understood to imply the exercise of a peculiar intellectual power, but which, in the case of attention to objects of sense, appears to be nothing more than the coexistence of desire, with the perception of the object to which we are said to attend; as, in attention to other phenomena of the mind, it is, in like manner, the coexistence of a particular desire with these particular phenomena. The desire, indeed, modifies the perception, rendering our feeling more intense, as any other emotion would do, that has equal relation to the object. But there is no operation of any power distinct from the desire and perception themselves.
To understand this fully, however, it may be necessary to make some previous remarks on the coexistence of sensations.
In the circumstances in which we are placed by our beneficent Creator, in a world of objects capable of exciting in us various feelings, and with senses awake to the profusion of delight,—breathing and moving in the midst of odours, and colours, and sounds, and pressed alike in gentle reaction, whether our limbs be in exercise or repose, by that firm soil which supports us, or the softness on which we rest,—in all this mingling action of external things, there is scarcely a moment in which any one of our feelings can be said to be truly simple.
Even when we consider but one of our organs, to the exclusion of all the others, how innumerable are the objects that concur in producing the complex affections of a single sense? In the eye, for example, how wide a scene is open to us, wherever our glance maybe turned?—woods, fields, mountains, rivers, the whole atmosphere of light, and that magnificent luminary, which converts into light the whole space through which it moves, as if incapable of existing but in splendour. The mere opening of our eyelid is like the withdrawing of a veil, which before covered the universe:—It is more; it is almost like saying to the universe, which had perished, Exist again!
Innumerable objects, then, are constantly acting together on our organs of sense; and it is evident, that many of these can, at once, produce an effect of some sort in the mind, because we truly perceive them as a coexisting whole. It is not a single point of light only which we see, but a wide landscape; and we are capable of comparing various parts of the landscape with each other,—of distinguishing various odours in the compound fragrance of the meadow or the garden,—of feeling the harmony of various coexisting melodies.
The various sensations, then, may coexist, so as to produce one complex affection. When they do coexist, it must be remarked, that they are individually less intense. The same sound, for example, which is scarcely heard in the tumult of the day, is capable of affecting us powerfully if it recur in the calm of the night; not that it is then absolutely louder, but because it is no longer mingled with other sounds, and other sensations of various kinds, which rendered it weaker, by coexisting with it. It may be regarded, then, as a general law of our perceptions, that when many sensations coexist, each individually is less vivid than if it existed alone.
It may be considered almost as another form of the same proposition to say, that when many sensations coexist, each is not merely weaker, but less distinct from the others with which it is combined. When a few voices sing together, we easily recognize each separate voice. In a very full chorus, we distinguish each with more difficulty; and, if a great multitude were singing together, we should scarcely be able to distinguish any one voice from the rest, more than to distinguish the noise of a single billow, or a single dashing of a few particles of agitated air, in the whole thunders of the ocean and the storm.
When many sensations coexist, and are, therefore, of course weaker and less distinct, if any one were suddenly to become much more intense, the rest would fade in proportion, so as scarcely to be felt. A thousand faint sounds murmur around us, which are instantly hushed by any loud noise. If, when we are looking at the glittering firmament of suns in a winter night, any one of those distant orbs were to become as radiant as our own sun, which is itself but the star of our planetary system, there can be no question, that, like our sun on its rising, it would quench with its brilliancy, all those little glimmering lights, which would still shine on us, indeed, as before, but would shine on us without being perceived. It may be regarded, then, as another general law of the mind, that when many sensations coexist of equal intensity, the effect of the increased intensity of one is a diminished intensity of those which coexist with it.