Tragedy is the imitation of a _serious_ action, that is, an action both grave and great, or, as the sixteenth century translated the word, illustrious. Now, what constitutes a serious action, and what actions are not suited to the dignified character of tragedy? Daniello (1536) distinguishes tragedy from comedy in that the comic poets "deal with the most familiar and domestic, not to say base and vile operations; the tragic poets, with the deaths of high kings and the ruins of great empires."[110] Whichever of these matters the poet selects should be treated without admixture of any other form; if he resolves to treat of grave matters, mere loveliness should be excluded; if of themes of loveliness, he should exclude all grave themes. Here, at the very beginning of dramatic discussion, the strict separation of themes or _genres_ is advocated in as formal a manner as ever during the period of classicism; and this was never deviated from, at least in theory, by any of the writers of the sixteenth century. Moreover, according to Daniello, the dignified character of tragedy demands that all unseemly, cruel, impossible, or ignoble incidents should be excluded from the stage; while even comedy should not attempt to represent any lascivious act.[111] This was merely a deduction from Senecan tragedy and the general practice of the classics. There is, in Daniello's theory of tragedy, no single Aristotelian element, and it was not until about a decade later that Aristotle's theory of tragedy played any considerable part in the literary criticism of the sixteenth century. In 1543, however, the _Poetics_ had already become a part of university study, for Giraldi Cintio, in his _Discorso sulle Comedie e sulle Tragedie_, written in that year, says that it was a regular academic exercise to compare some Greek tragedy, such as the _Oedipus_ of Sophocles, with a tragedy of Seneca on the same subject, using the _Poetics_ of Aristotle as a dramatic text-book.[112] Giraldi distinguishes tragedy from comedy on somewhat the same grounds as Daniello. "Tragedy and comedy," he says, "agree in that they are both imitations of an action, but they differ in that the former imitates the illustrious and royal, the latter the popular and civil. Hence Aristotle says that comedy imitates the worse sort of actions, not that they are vicious and criminal, but that, as regards nobility, they are worse when compared with royal actions." Giraldi's position is made clear by his further statement that the actions of tragedy are called illustrious, not because they are virtuous or vicious, but merely because they are the actions of people of the highest rank.[113]