Yet much of poetry is unfit for union with music. This is true, first, of all highly intellectual poetry, where the emotions are embodied in complex and abstract ideas. One could not, for example, readily set Browning to music. Music may be deep, mystic, even metaphysical in its meaning, but it cannot be dialectical. The emotions that accompany subtle thought, even when intense, are not of the voluminous, massive kind which music expresses; they lack the bodily resonance of the latter; they are, moreover, clean-cut and static, while in music everything flows in half-lights, like a river moving in moonlight. On the other hand, poems which express rapidly developing states of mind, which contain quick, subtle transitions, are equally unfit for union with music. For music, although always in motion, is always in slow motion; it needs time to get under way, and time for its development in embroidering, varying, and repeating its theme. And this difficulty applies in a general way to every union between poetry and music. For words are primarily practical and communicative, and therefore cut short the passion which they express; whereas tones, never having had any other purpose than expression, draw it out and let it have its way. Moreover, poetry, because of its definiteness, is compatible with only a limited range of variation, beyond which it becomes monotonous, while music, because of its abstractness, permits of variations almost endless, and is enriched by every new shape in which its meaning can appear. If, therefore, poetry is to keep time with the slow movement of the music and conform to its mode of development, the verses have to be repeated again and again; but this destroys the poetic form--as in the oratorio, with its senseless iterations.