9. Attention is the application of the mind to something; and this application supposes the exercise of an activity concentrated upon its object. Properly speaking, when the mind holds itself entirely passive, it is not attentive; and with respect to sensations it is attentive when by a reflex act we know that we feel. Without this cognition there can be no attention, but only sensation more or less active, according to the degree in which it affects our sensibility. If Condillac means to call the more vivid sensation attention, the word is improperly used; for it ordinarily happens that they who feel with the greatest vividness are precisely those who are distinguished for their want of attention. Sensation is the affection of a passive faculty; attention is the exercise of an activity; and hence it is that brutes do not participate of it except inasmuch as they possess a principle of activity to direct their sensitive faculties to a determinate object. 10. Is the perception of the difference of the smell of the rose and that of the pink a sensation? If we are answered that it is not, we infer that the judgment is not the sensation transformed; for it is not even a sensation. If we are told that it is one sensation, we then observe that if it be either that of the rose or that of the pink, it follows that with one alone of these sensations we shall have comparative perception, which is absurd. If we are answered that it is both together, we must either interpret this expression rigorously, and then we shall have a sensation which will at once be that of the pink and that of the rose, the one remaining distinct from the other so as to satisfy the conditions of comparison; or we must interpret it so as to mean that the two sensations are united; in which case we gain nothing, for the difficulty will be to show how co-existence produces comparison, and judgment, or the perception of the difference. The sensation of the pink is only that of the pink, and that of the rose only that of the rose. The instant you attempt to compare them, you suppose in the mind an act by which it perceives the difference; and if you attribute to it any thing more than pure sensation, you add a faculty distinct from sensation, namely that of comparing sensations, and appreciating their similarities and differences. 11. This comparison, this intellectual force, which calls the two extremes into a common arena, without confounding them, discovers the points in which they are alike or unlike each other, and, as it were, comes in and decides between them, is distinct from the sensation; it is the effect of an activity of a different order, and its development must depend on sensations as exciting causes, as a condition _sine qua non_; but this is all it has to do with sensations themselves; it is essentially distinct from them, and cannot be confounded with them without destroying the idea of comparison, and rendering it impossible.