Didactic in another kind is that short _Art of Poetry_, written in deft verse by Horace, which was copied by Boileau in his _Art Poétique_, and freely utilized by Pope in his _Essay on Criticism_. Its professed aim is to inculcate certain principles of poetic composition, and, in particular, the composition of drama. Inasmuch as Horace was drawing upon Greek doctrines derived from Aristotle, but not always understood by their somewhat superficial Roman poetizer; inasmuch also as poetic drama had no real existence in the days of Horace, there was little prospect that the _Art of Poetry_ would shed any new illumination upon the world. To those who have read the seminal work of Aristotle, the precepts of Horace inevitably appear rather trite and shallow. The writer here, as elsewhere, is marked by shrewd and humorous good sense and a gift of terse expression, and it must be admitted that these form an excellent endowment for the middleman of intellectual traffic. The essay would doubtless be read by his contemporaries with enjoyment, and in many cases with edification. The misfortune is that, from the later seventeenth century onwards, it was the superficial Horace rather than the fundamental Aristotle who served as dictator of the laws of verse to both England and France. Philosophic verse, which is, of course, a species of the didactic, finds its best representative, not merely for Latin literature, but for the literature of the world, in Lucretius, who wrote during the latter days of republican Rome. His poem _On the Nature of Things_ is an exposition of the philosophy of Epicurus, as developed from the physical speculations of Democritus. According to this philosophy the original contents of the universe were minute atoms, the “seeds” or “elements” of things, moving in a void. By their fortuitous collisions and various combinations were formed all things as they are or have been. To this extent had ancient speculation, combining bold imagination with close reasoning, anticipated modern chemistry and astronomical hypothesis. From crude and accidental beginnings, says Lucretius, there ensues a “survival of the fittest,” and thus, though unaided by modern scientific appliances, and imperfectly directed from the point of view of modern scientific method, ancient speculation anticipates also the doctrines of modern evolutionists. In the application of these results to the conduct of life (which is the practical aim of philosophy) it is evident that current theology must receive a severe blow. To Lucretius the chief blessing derived from the true philosophy is that man is emancipated from superstition, with all its terrors in life and death and all the mischiefs it has worked. We may conjecture that the soul of the poet himself, which was brooding and melancholy, would have been eminently impressible by superstitious dread, if it had not been fortified by this wisdom of “the master.” His fervent onslaught on _religio_ (in the Latin