Even though we should be incapable, therefore, of understanding how the desire should have this effect, it would not be the less true, that the desire of knowing accurately a particular object in a group, is instantly,—or, at least, instantly after some organic change which may probably be necessary,—followed by a more vivid and distinct perception of the particular object, and a comparative faintness and indistinctness of the other objects that coexist with it; and that what we call attention is nothing more.
Are the comparative distinctness and indistinctness, however, a result which we had no reason to expect? or are they not rather what might, in some degree at least, have been expected, from our knowledge of the few physical facts with respect to our co-existing sensations, which I have already pointed out to you, and from the circumstance which we are next to consider? We have seen, in the observations already made by us, that many co-existing perceptions are indistinct, and that when one becomes more vivid, the others become still fainter. All that is necessary, therefore, is to discover some cause of increased vividness of that one to which we are said to attend.
If we can discover any reason why this should become more vivid, the comparative indistinctness of the other parts of the scene may be considered as following of course.
Such a cause exists, unquestionably, in that feeling of desire, without which there can be no attention. To attend, is to have a desire of knowing that to which we attend, and attention without desire is a verbal contradiction,—an inconsistency, at least, as great as if we were said to desire to know without any desire of knowing, or to be attentive without attention.
When we attend, then, to any part of a complex group of sensations, there is always an emotion of desire, however slight the emotion may be, connected exclusively with that particular part of the group to which we attend; and whatever effect our emotions produce on the complex feelings that accompany them, we may expect to be produced, in some greater or less degree, by the desire in the complex process which we term attention.
The effect which our expectation might anticipate, is the very effect that is truly found to take place,—an increased liveliness of that part of the complex group, to which alone the desire relates.
That it is the nature of our emotions of every sort, to render more vivid all the mental affections with which they are peculiarly combined, as if their own vivacity were in some measure divided with these, every one who has felt any strong emotion, must have experienced. The eye has, as it were, a double quickness, to perceive what we love or hate, what we hope or fear. Other objects may be seen slightly; but these, if seen at all, become instantly permanent, and cannot appear to us without impressing their presence, as it were, in stronger feeling on our senses and our soul.
Such is the effect of emotion, when combined even with sensations that are of themselves, by their own nature, vivid; and mark, therefore, less strikingly, the increase of vividness received. The vivifying effect, however, is still more remarkable, by its relative proportion, when the feelings with which the emotion is combined, are in themselves peculiarly faint, as in the case of mere memory or imagination. The object of any of our emotions, thus merely conceived by us, becomes, in many cases, so vivid, as to render even our accompanying perceptions comparatively faint. The mental absence of lovers, for example, is proverbial; and what is thus termed in popular language absence, is nothing more than the greater vividness of some mere conception, or other internal feeling, than of any, or all of the external objects present at the time, which have no peculiar relation to the prevailing emotion.
“The darkened sun