An art, therefore, however abstract, like Music or like the decorative pattern in a Celtic MS., which expressed the union of these two principles might be profoundly expressive of life. It need not set before us any definite living thing provided it expresses the cardinal principles of all life. It will do this the better the more intimately these principles are blended, as in nature, into a vital unity. On the other hand, art does, of course, frequently represent individual objects, and probably had its first distinguishable beginnings in so doing.[180] We may, then, get a broad classification of the arts by placing on one side those which deal with objects of sense, and on the other those which convey life under forms devised by the artist himself, and not found in the external world. One is tempted to call these respectively Imitative and Creative. But, after all, what is essentially artistic in the first category is just the fact that it is _not_ purely imitative, for, as Mr. Whistler observed, to suppose that you can get art by copying nature is equivalent to thinking that you can get music by sitting on the piano. On the other hand, it does not seem fitting to use so exalted a word as creation with reference to the pattern which a Zuñi Indian draws on a piece of pottery, while denying it to a painting by Titian. Instead, therefore, of using the words Creative and Imitative—now that we know what we mean by them—we shall contrast those arts which are directly Presentative with those which are Representative. In the one case the artist presents us with the whole artistic product, form and substance, as devised by himself. In the other, he represents to us forms already presented by nature, but re-composed, re-presented, and harmonized by him for an æsthetic purpose. The Presentative arts fall into two classes. In one of these Music stands alone. Here the artistic purpose is not only dominant but (I speak, of course, of music in its highest and most characteristic development) there is no other purpose whatever. The forms elaborated by combinations and sequences of sound have no object except that of art and mean nothing apart from that. Hence Music has been called ‘pure style.’ We shall recur to this subject when we have dealt with the other class, that of the Decorative arts, the essence of which it is to add an expression of rhythm, of world-harmony, to objects whose primary purpose is something different—a building, a vase, a piece of furniture, or a hanging. This class, again, can be subdivided into arts which attain this effect by the structure of the object, and those which do so by the application of ornament to its surface; both being, of course, often combined in the same object.