Theater has its roots in ancient Greece. The Greek philosopher Aristotle studied earlier plays as well as those of his time and developed his rules for the composition of tragedy. Aristotle established these guidelines in his work “Poetics” in the fourth century B.C.E.
In his "Poetics," Aristotle examined plays as a separate art form and discussed how they differed from epic poetry. He deduced the elements that created a successful tragedy. Aristotle’s guidelines became the basis for dramatic composition for the next two thousand years. Among these ideas, he advocated the unity of time, place and action.
Unity of Time
Aristotle proposed that the action of a play should take place within a short period of time, covering no more than twenty-four hours. Real-time performances captured the audience’s attention and created a sense of immediacy. The characters may refer to events outside the time period of the play in order to set the tone and context of the performance. However, ideally, the actual action of the play should be contained within the time limits of the play itself.
Unity of Place
Aristotle contended that plays should take place in only one setting. He felt that moving from one location to another was confusing to the audience and distracted from the plot. The plot, to his way of thinking, was the most important aspect of the performance. Characters, setting and other elements were considered secondary to the strong flow of action leading inevitably to a conclusion.
Unity of Action
Unity of action refers to Aristotle’s contention that a play should contain one central plot or theme and a clear beginning, middle and end. He considered the worst plot to be made up of a string of episodes; it lacked the "cause and effect" that a true plot should have. All scenes within the play should further the plot; digressions should be discouraged. Nothing random or illogical should break up the flow of the action. Aristotle was particularly critical of using divine intervention to extricate characters from their circumstances. This was the practice of having a god appear at the end of the play to sort out the problems created by the actions of the characters or to resolve a situation.
One must remember that Aristotle was providing these ground rules during the fourth century B.C.E. At the time, plays were performed outdoors and the use of multiple settings would be expensive and complicated to produce. The audience would likely get confused in the process of changing sets and props, since there were no such things as playbills to announce the change of scene. Finally, Aristotle was known as a philosopher who relished logic. Any dramatic progression that lay outside the realm of logic would have been anathema to him. It is important to keep the historical and personal context of these rules in mind when considering their implications.