(_a_) Otherwise expressed, by reason of the importance pertaining to the material aspect in the plastic arts and music, we find that, as a result of the _defined_ restrictions of this material, only a _limited_ number of conceptions can be fully reproduced in a particularized form of reality such as stone, colour, and tone: the content therefore and the possibilities of artistic composition are narrowed within very definable limits. It was on account of this fact that we were able to associate closely and exclusively every one of these specific arts with one particular form of artistic creation pre-eminently adapted to it. In this way the form of symbolism was appropriate to architecture, the classical to sculpture, and the romantic to painting and music. It is no doubt true that the particular arts in both directions from and toward their proper domain tended to pass over into the other forms. We took account of this fact when we found it possible to refer to a classic and romantic style of architecture, a symbolical and Christian type of sculpture, and even used the term classic in connection with painting and music. Departures such as these from the prevailing type were, however, merely experimental essays which prepared the way in subordination to a new type rather than its culminating effort; or they showed us how one art tended to pass beyond its true limits in seeking to grasp a content or a relation to its material of a type that only a further art development could adequately elaborate. Generally speaking, we have seen that architecture has least resource in the expression of its content; in sculpture there is already an increase of possibility, which is further extended to its widest range[9] by painting and music. And the reason of this is that in proportion as the ideality and particularization under all its aspects by the external medium is made more explicit the variety of the content and of the forms it receives also increases. Poetry, on the other hand, casts itself free of all subordination to the material of sense, at least to this extent, that in the definition of external or objective expression no reason whatever remains why it should restrict itself to specific content or any limitation to its power of composition and reproduction. It is therefore exclusively united to no specific art type; rather we may define it as the _universal_ art, which is capable of reclothing and expressing under every conceivable mode every content that can possibly enter into or proceed from the imagination of man. And it can do this because its material is nothing more or less than the imagination itself, which is the universal root and ground of all the particular arts and their specific types.