Nearly ten years elapsed between the publication of the second book of the _Satires_ and that of the first book of the _Epistles_. Horace had passed meanwhile into later middle life. He had in great measure retired from society, and lived more and more in the quietness of his little estate among the Sabine hills. Life was still full of vivid interest; but books were more than ever a second world to him, and, like Virgil, he was returning with a perpetually increasing absorption to the Greek philosophies, which had been the earliest passion of his youth. Years had brought the philosophic mind; the more so that these years had been filled with the labour of the _Odes,_ a work of the highest and most intricate effort, and involving the constant study of the masterpieces of Greek thought and art. The "monument more imperishable than bronze" had now been completed; its results are marked in the _Epistles_ by a new and admirable maturity and refinement. Good sense, good feeling, good taste, --these qualities, latent from the first in Horace, have obtained a final mastery over the coarser strain with which they had at first been mingled; and in their shadow now appear glimpses of an inner nature even more rare, from which only now and then he lifts the veil with a sort of delicate self-depreciation, in an occasional line of sonorous rhythm, or in some light touch by which he gives a glimpse into a more magical view of life and nature: the earliest swallow of spring on the coast, the mellow autumn sunshine on a Sabine coppice, the everlasting sound of a talking brook; or, again, the unforgettable phrases, the _fallentis semita vitae,_ or _quod petis hic est,_ or _ire tamen restat,_ that have, to so many minds in so many ages, been key-words to the whole of life.