Introductions to forensic speeches, it must be observed, have the same value as the prologues of dramas and the introductions to epic poems; the dithyrambic prelude resembling the introduction to a speech of display, as
"For thee, and thy gilts, and thy battle-spoils.... "
In prologues, and in epic poetry, a foretaste of the theme is given, intended to inform the hearers of it in advance instead of keeping their minds in suspense. Anything vague puzzles them: so give them a grasp of the beginning, and they can hold fast to it and follow the argument. So we find-
"Sing, O goddess of song, of the Wrath...
"Tell me, O Muse, of the hero...
"Lead me to tell a new tale, how there came great warfare to Europe
"Out of the Asian land... "
The tragic poets, too, let us know the pivot of their play; if not at the outset like Euripides, at least somewhere in the preface to a speech like Sophocles-
"Polybus was my father...; "
and so in Comedy. This, then, is the most essential function and distinctive property of the introduction, to show what the aim of the speech is; and therefore no introduction ought to be employed where the subject is not long or intricate.