The foregoing distinctions among passions and emotions, may serve the common affairs of life, but they are not sufficient for the critical art. The qualities of pleasant and painful are too familiar to carry us far into human nature, or to form an accurate judgement in the fine arts. It is further necessary, that we be made acquainted with the several modifications of these qualities, with the modifications at least that make the greatest figure. Even at first view every one is sensible, that the pleasure or pain of one passion differs from that of another. How distant the pleasure of revenge from that of love? So distant, as that we cannot without reluctance admit them to be any way related. That the same quality of pleasure should be so differently modified in different passions, will not be surprising, when we reflect on the boundless variety of pleasant sounds, tastes, and smells, daily felt. Our discernment reaches differences still more nice, in objects even of the same sense. We have no difficulty to distinguish different sweets, different sours, and different bitters. Honey is sweet, and so is sugar; and yet they never pass the one for the other. Our sense of smelling is sufficiently acute, to distinguish varieties in sweet-smelling flowers without end. With respect to passions and emotions, their different feelings have no limits; for when we attempt the more delicate modifications, they elude our search, and are scarce discernible. In this matter, however, there is an analogy betwixt our internal and external senses. The latter generally are sufficiently acute for all the useful purposes of life, and so are the former. Some persons indeed, Nature’s favourites, have a wonderful acuteness of sense, which to them unfolds many a delightful scene totally hid from vulgar eyes. But if such refined pleasure be refused to the bulk of mankind, it is however wisely ordered that they are not sensible of the defect; and it detracts not from their happiness that others secretly are more happy. With relation to the fine arts only, this qualification seems essential; and there it is termed _delicacy of taste_. Should an author of such a taste attempt to describe all those differences and shades of pleasant and painful emotions which he himself feels, he would soon meet an invincible obstacle in the poverty of language. No known tongue hitherto has reached such perfection, as to express clearly the more delicate feelings. A people must be thoroughly refined, before their language become so comprehensive. We must therefore rest satisfied with an explanation of the more obvious modifications. In forming a comparison betwixt pleasant passions of different kinds, we conceive some of them to be _gross_ some _refined_. Those pleasures of external sense that are felt as at the organ of sense, are conceived to be corporeal or gross[31]. The pleasures of the eye and ear are felt to be internal; and for that reason are conceived to be more pure and refined.