In another place Castelvetro more briefly formulates the law of the unities in the definitive form in which it was to remain throughout the period of classicism: "La mutatione tragica non puo tirar con esso seco se non una giornata e un luogo."[193] The unities of time and place are for Castelvetro so very important that the unity of action, which is for Aristotle the only essential of the drama, is entirely subordinated to them. In fact, Castelvetro specifically says that the unity of action is not essential to the drama, but is merely made expedient by the requirements of time and place. "In comedy and tragedy," he says, "there is usually one action, not because the fable is unfitted to contain more than one action, but because the restricted space in which the action is represented, and the limited time, twelve hours at the very most, do not permit of a multitude of actions."[194] In a similar manner Castelvetro applies the law of the unities to epic poetry. Although the epic action can be accomplished in many places and at diverse times, yet as it is more commendable and pleasurable to have a single action, so it is better for the action to confine itself to a short time and to but few places. In other words, the more the epic attempts to restrict itself to the unities of place and time, the better, according to Castelvetro, it will be.[195] Moreover, Castelvetro was not merely the first one to formulate the unities in their definitive form, but he was also the first to insist upon them as inviolable laws of the drama; and he refers to them over and over again in the pages of his commentary on the _Poetics_.[196]