Shelley, we may safely say, did not understand the real constitution of nature. It was hidden from him by a cloud, all woven of shifting rainbows and bright tears. Only his emotional haste made it possible for him to entertain such, opinions as he did entertain; or rather, it was inevitable that the mechanism of nature, as it is in its depths, should remain in his pictures only the shadowiest of backgrounds. His poetry is accordingly a part of the poetry of illusion; the poetry of truth, if we have the courage to hope for such a thing, is reserved for far different and yet unborn poets. But it is only fair to Shelley to remember that the moral being of mankind is as yet in its childhood; all poets play with images not understood; they touch on emotions sharply, at random, as in a dream; they suffer each successive vision, each poignant sentiment, to evaporate into nothing, or to leave behind only a heart vaguely softened and fatigued, a gentle languor, or a tearful hope. Every modern school of poets, once out of fashion, proves itself to have been sadly romantic and sentimental. None has done better than to spangle a confused sensuous pageant with some sparks of truth, or to give it some symbolic relation to moral experience. And this Shelley has done as well as anybody: all other poets also have been poets of illusion. The distinction of Shelley is that his illusions are so wonderfully fine, subtle, and palpitating; that they betray passions and mental habits so singularly generous and pure. And why? Because he did not believe in the necessity of what is vulgar, and did not pay that demoralising respect to it, under the title of fact or of custom, which it exacts from most of us. The past seemed to him no valid precedent, the present no final instance. As he believed in the imminence of an overturn that should make all things new, he was not checked by any divided allegiance, by any sense that he was straying into the vapid or fanciful, when he created what he justly calls “Beautiful idealisms of moral excellence.”