Dryden’s Essay of Dramatic Poesy is a discussion in dialogue form of such matters as the merits of Elizabethan, French, and Restoration plays, the place of rhyme in drama, and the value of dramatic “rules.” It is said that the unity of time the audience can comprehend is about 24 hours or as close to that as they can come. The reasoning behind this is the fact the pretend action, or plot of the story should be about the same as the time that it is representing, or as close as possible. By doing this the viewer of the play is not getting what he or her should be. By limiting the amount of time that can be represented in a play, you are limiting the potential of the writer. And by doing this you are not giving the viewer what they want, a good show.
The unity of place is where the play is set, where the action takes place. This unity says that the play should have a consistent setting. Since the stage on which the play is performed is only one stage, it is inconceivable that it be thought of as many different ones, far apart or near to each other. If the setting varied in position, being far apart, would not hold true to the unity of time. If you were to travel to other cities or countries it would surely take longer than twenty-four hours. The French follow this strictly, a scene is never changed in the middle of an act. If the act begins in a bedroom or on a street that is where it is going to end.
The third unity touched upon is the unity of action. The unity of action says that there is only room in one play for one major action. That action is to be the aim of the play. Everything in the play has to do with the completion of this action. If there are two actions in one play it is not one play, it is then two. This does not mean there cannot be many actions in the play.
It means that all these actions must have something to do with the overall, also know as sub-plots. If there is one main action and that action is completed then the audience know exactly what is going on. But if there are sub-plots and other things that are not fully completed then there will be an element of suspense, it will keep the audience interested. If we were to compare literature of his time to these unities, I would bet, very few of them would measure up. For example Shakespeare, look at any one of his works.
The unity of time is completely forgotten, some of his works are stretched on for generations. Settings in one play go from one country to another, city to city. And the actions in his plays can sometimes be the actions of a mans entire life. So in short, John Dryden is saying that the three unities can be, and are, forgotten.