The Cambridge History of English and American Literature in 18 Volumes (1907–21). Volume XII. The Romantic Revival. IV. Keats. § 3. Isabella; Letters. Great as is the advance of Isabella upon Endymion, it must still be reckoned among his immature works, in view of the wonderful creations of the following autumn and spring. The six months which followed were a time of immensely rapid growth, not merely in imaginative power and technical mastery, but in intellectual range and vigour, and in moral grip. The not very precocious boy of eighteen and twenty is on the verge of the truly marvellous manhood of his twenty-fourth year, and the man, as well as the genius, is awake. His letters, after The Prelude the most precious document we possess of the growth of a poet’s mind, are especially illuminating for the year 1818. “To enjoy the things that others understand” might have satisfied his aspiration in 1817; in April, 1818, he turns away dissatisfied from his own “exquisite sense of the luxurious,” and feels the need of “philosophy,” bracing experience and activity for his fellow-men. He will learn Greek and Italian, and in other ways prepare myself to ask Hazlitt in about a year’s time the best metaphysical road I can take…. I find there is no worthy pursuit but the idea of doing some good in the world. In July, during a foot-tour with his friend Brown through the Highlands, he writes: I should not have consented to these four months’ tramping,… but that I thought it would give me more experience, rub off more prejudice, use me to more hardship, identify finer scenes, load me with grander mountains, and strengthen more my reach in poetry than would stopping at home among my books. The germ of such thoughts can be found, it is true, in much earlier letters, and, as we have seen, in his first poetic profession of faith; for Keats was at no time the weakling suggested by much of his youthful verse. But they are pronounced with new conviction, they mark no fugitive aspiration, but a spiritual deliverance already, in effect, accomplished.   7   He had, indeed, “great allies”; Shakespeare and Wordsworth co-operated in deepening and enlarging the scope of his genius; to its richness they could not add. All through 1817, Shakespeare had been a companion; Endymion is strewn with his diction; in April, 1818 (sonnet On sitting down to read King Lear once again), the golden harmonies of romance seemed thin and poor beside the passion and the heights and depths of Shakespearean tragedy. He was already past Endymion, and knew it, as his contemporary preface attests. And Wordsworth led him, by other, not less enthralling or less enduring, paths, to the same deeper understanding of sorrow. He was never weary, Brown tells us, of repeating the Immortality ode; its sublime portrayal of a mind redeemed by discipline and suffering and “an eye that hath kept watch o’er man’s mortality” perhaps contributed to the doctrine of the world as a “Vale of Soul-making” through pain and trouble, which he unfolds in his beautiful letter of April, 1819, to his brother George.   8