It was doubtless the necessity for marking this rhythm that Aristotle had in mind when he said that a dramatic action must have a beginning, a middle and an end.  Taken in its simplicity, this principle would indicate the three-act division as the ideal scheme for a play.  As a matter of fact, many of the best modern plays in all languages fall into three acts; one has only to note Monsieur Alphonse, Francillon, La Parisienne, Amoureuse, A Doll’s House, Ghosts, The Master Builder, Little Eyolf, Johannisfeuer, Caste, Candida, The Benefit of the Doubt, The Importance of Being Earnest, The Silver Box; and, furthermore, many old plays which are nominally in five acts really fall into a triple rhythm, and might better have been divided into three.  Alexandrian precept, handed on by Horace, gave to the five act division a purely arbitrary sanction, which induced playwrights to mask the natural rhythm of their themes beneath this artificial one.[2] But in truth the three-act division ought no more to be elevated into an absolute rule than the five-act division.  We have seen that a play consists, or ought to consist, of a great crisis, worked out through a series of minor crises.  An act, then, ought to consist either of a minor crisis, carried to its temporary solution, or of a well-marked group of such crises; and there can be no rule as to the number of such crises which ought to present themselves in the development of a given theme.  On the modern stage, five acts may be regarded as the maximum, simply by reason of the time-limit imposed by social custom on a performance.  But one frequently sees a melodrama divided into “five acts and eight tableaux,” or even more; which practically means that the play is in eight, or nine, or ten acts, but that there will be only the four conventional interacts in the course of the evening.  The playwright should not let himself be constrained by custom to force his theme into the arbitrary mould of a stated number of acts.  Three acts is a good number, four acts is a good number,[3] there is no positive objection to five acts.  Should he find himself hankering after more acts, he will do well to consider whether he be not, at one point or another, failing in the art of condensation and trespassing on the domain of the novelist.

There is undoubted convenience in the rule of the modern stage:  “One act, one scene.”  A change of scene in the middle of an act is not only materially difficult, but tends to impair the particular order of illusion at which the modern drama aims.[4] Roughly, indeed, an act may be defined as any part of a given crisis which works itself out at one time and in one place; but more fundamentally it is a segment of the action during which the author desires to hold the attention of his audience unbroken and unrelaxed.  It is no mere convention, however, which decrees that the flight of time is best indicated by an interact.  When the curtain is down, the action on the stage remains,