The Bedford Glossary of Critical and Literary Terms - Ross Murfin 2018
Unities: A set of three structural principles for drama calling for unity of action, time, and place. Unity of action was a rule of plot requiring that the work present a single, continuous action without extraneous subplots. Unity of time mandated that the action occur within a single day, unity of place that it occur within one location. The three unities were intended as devices to assure verisimilitude; literary critics claimed that a play, performed of necessity in one place over a few hours, could not seem realistic if its action took place in a number of settings over long periods of time.
Although the unities are often ascribed to the ancient Greek philosopher Aristotle, particularly to his Poetics (c. 330 B.C.), Aristotle emphasized only unity of action, writing that “the plot, being an imitation of an action, must imitate one action and that a whole, the structural union of the parts being such that, if any one of them is displaced or removed, the whole will be disjointed and disturbed.” With regard to time, he observed that “Tragedy endeavors … to confine itself to a single revolution of the sun, or but slightly to exceed this limit” but did not prescribe such a limit. He did not discuss unity of place.
It was Italian and French critics of the sixteenth and seventeenth centuries who, expanding on — or misreading — Aristotle, developed the unities of time and place and established all three unities as prescriptive rules. In Italy, Renaissance critic Lodovico Castelvetro formulated the unities in 1570 in translating and analyzing the Poetics. In France, neoclassical playwright Jean Mairet is generally credited with introducing the unities, which he strictly observed in his play Sophonisbe (1634). Unity of time was often interpreted as requiring that the action take place over a period of no more than twenty-four hours; some critics, however, limited the period to twelve hours or even to the length of time needed to perform the play itself. Unity of place, narrowly interpreted, meant confining the action to one specific place; more broadly interpreted, to one city.
A dramatist failing to adhere to the unities risked not only critical condemnation but even the banishment of the “offending” play from the stage. So seriously was the requirement taken that when rivals accused French playwright Pierre Corneille of violating these rules in Le Cid (1636), Cardinal Richelieu ordered the Académie Française (the French Academy of Letters) to settle the bitter quarrel. After prolonged deliberation, the Académie concluded that Corneille had in fact violated the putatively classical rules, although it conceded that the passion, force, and charm of the play had earned it both public adulation and a considerable place in French theater.
In England, a few seventeenth-century dramatists (such as Francis Beaumont and John Fletcher) attempted to adopt or, at least, adapt the unities, but, unlike the French and the Italians, the English generally ignored them. Subsequently, in all three countries, the unities — save perhaps unity of action — were largely abandoned with the waning of neoclassicism and the rise of romanticism.