A regular dictionary has maybe 50,000 entries; a good one has 100,000 entries. The Oxford English Dictionary has half a million entries—every word used in the English language since Chaucer. It does more than define words; it gives definitions across time, tracking changes in the usage of a single word across centuries, illustrated with quotations from the literature of each historical period. The OED is important in the study of poetry, because poets are sensitive to the history of words and invoke that history to get the most charge out of the language. Robert Frost’s “Directive,” for example, describes leading the reader to a secret goblet of which he may “[d]rink and be whole again beyond confusion” (379). In his book Genius, literary critic Harold Bloom remarks, “Frost . . . seem[s] to have known that the Indo-European root of ‘confusion’ initially signified the pouring of a libation to the gods” (361). The history of the word comes into play to determine the meaning of the poem.

Just as poets think across time to chose the word that will bring, in its history, the proper meanings to a poem, a good casting director will select an actor that carries, in his career, the best meanings for a show.

Steve Martin, for example, is a fascinating choice to play the villain in David Mamet’s The Spanish Prisoner—as a con man we feel there is something going on beneath the surface of this character; a comedian in a straight role is an interesting way  …