Introduced by Francis Fergusson, the Poetics, written in the fourth century B.C., is still an essential study of the art of drama, indeed the most fundamental one we have. It has been used by both playwrights and theorists of many periods, and interpreted, in the course of its two thousand years of life, in various ways. The literature which has accumulated around it is, as Mr. Fergusson points out, "full of disputes so erudite that the nonspecialist can only look on in respectful silence." But the Poetics itself is still with us, in all its suggestiveness, for the modern...