That is what his poems are fundamentally--the _Skylark_, and the _Witch of the Atlas_, and the _Sensitive Plant_ no less than the grander pieces. He infused into his gossamer world the strength of his heroic conscience. He felt that what his imagination pictured was a true symbol of what human experience should and might pass into. Otherwise he would have been aware of playing with idle images; his poetry would have been mere millinery and his politics mere business; he would have been a worldling in art and in morals. The clear fire, the sustained breath, the fervent accent of his poetry are due to his faith in his philosophy. As Mrs. Shelley expressed it, he "had no care for any of his poems that did not emanate from the depths of his mind, and develop some high and abstruse truth." Had his poetry not dealt with what was supreme in his own eyes, and dearest to his heart, it could never have been the exquisite and entrancing poetry that it is. It would not have had an adequate subject-matter, as, in spite of Matthew Arnold, I think it had; for nothing can be empty that contains such a soul. An angel cannot be ineffectual if the standard of efficiency is moral; he is what all other things bring about, when they are effectual. And a void that is alive with the beating of luminous wings, and of a luminous heart, is quite sufficiently peopled. Shelley's mind was angelic not merely in its purity and fervour, but also in its moral authority, in its prophetic strain. What was conscience in his generation was life in him.