The essay on Beauty in the Encyclopaedia is less fertile than most of Diderot's contributions to the subject.[60] It contains a careful account of two or three other theories, especially that of Hutcheson. The object is to explain the source of Beauty. Diderot's own conclusion is that this is to be found in "relations." Our words for the different shades of the beautiful are expressive of notions (acquired by experience through the senses) of order, proportion, symmetry, unity, and so forth. But, after all, the real question remains unanswered--what makes some relations beautiful, and others not so; and the same objects beautiful to me, and indifferent to you; and the same object beautiful to me to-day, and indifferent or disgusting to me to-morrow? Diderot does, it is true, enumerate twelve sources of such diversity of judgment, in different races, ages, individuals, moods, but their force depends upon the importation into the conception of beauty of some more definite element than the bare idea of relation. Some sentences show that he came very near to the famous theory of Alison, that beauty is only attributed to sounds and sights, where, and because, they recall what is pleasing, sublime, pathetic, and set our ideas and emotions flowing in one of these channels. But he does not get fairly on the track of either Alison's or any other decisive and marking adjective, with which to qualify his _rapports_. He wastes some time, moreover, in trying to bring within the four corners of his definition some uses of the terms of beauty, which are really only applied to objects by way of analogy, and are not meant to predicate the beautiful in any literal or scientific sense. [60] _Oeuv._, x. There is no more interesting department of aesthetic inquiry than the relations of the arts to one another, and the nature of the delimitations of the provinces of poetry, painting, sculpture, music. Diderot, from the very beginning of his career, had turned his thoughts to this intricate subject. In his letter on Deaf Mutes (1751) he had stated the problem--to collect the common beauties of poetry, painting, and music; to show their analogies; to explain how the poet, the painter, and the musician render the same image; to seize the fugitive emblems of their expression. Why should a situation that is admirable in a poem become ridiculous in a painting?[61] For instance, what is it that prevents a painter from reproducing the moment when Neptune raises his head above the tossing waters, as he is represented in Virgil: Interea magno misceri murmure pontum. Emissamque hiemem sensit Neptunus, et imis Stagna refusa vadis; graviter commotus, et alto Prospiciens, summa placidum caput extulit unda.