Twice in his early maturity he wrote in verse on the theory of poetry. The first, in 1836, when he was entering the medical profession, was his Phi Beta Kappa poem "Poetry"; the second was "Urania," in 1846, shortly before he accepted his Harvard professorship. The object of "Poetry," he wrote in a preface for its publication, was "to express some general truths on the sources and the machinery of poetry; to sketch some changes which may be said to have taken place in its history, constituting four grand eras; and to point out some less obvious manifestations of the poetic principle." In old age he looked back on this ambitious early effort with kindly indulgence, and allowed it to stand as a matter of biographical interest, although it was so evidently the product "of a young person trained after the schools of classical English verse as represented by Pope, Goldsmith, and Campbell, with whose lines his memory was early stocked." When, however, he wrote "Urania, a Rhymed Lesson" he wore a friendly smile and did his teaching in a less didactic way. He knew his audience, he said, and he knew that they all expected to be amused. I know a tailor, once a friend of mine, Expects great doings in the button line,-- For mirth's concussions rip the outward case, And plant the stitches in a tenderer place, I know my audience,--these shall have their due; A smile awaits them ere my song is through! But, he went on to say, he knew himself, too, and he proposed no more to be the buffoon than to be the savage satirist. Beneath his smiles there was a kindly seriousness. A dozen years later, in the fifth of the "Autocrat" papers, he put the case in a little allegory, the end of which is worth quoting in full: The stone is ancient error. The grass is human nature borne down and bleached of all its color by it. The shapes which are found beneath are the crafty beings which thrive in darkness, and the weaker organisms kept helpless by it. He who turns the stone over is whosoever puts the staff of truth to the old lying incubus, no matter whether he do it with a serious face or a laughing one. The next year stands for the coming time. Then shall the nature which had lain blanched and broken rise in its full stature and native hues in the sunshine. Then shall God's minstrels build their nests in the hearts of a new-born humanity. Then shall beauty--Divinity taking outlines and color--light upon the souls of men as the butterfly, image of the beatified spirit rising from the dust, soars from the shell that held a poor grub, which would never have found wings, had not the stone been lifted.