Aristotle speaks of the mechane as the invariable device on such occasions. The phrase ‘deus ex machina’ appears already in the fourth century as a proverbial expression for an unexpected benefactor.[656] It seems more probable, therefore, that the mechane was regularly used, even in the fifth century, for the same purpose. We have several cases in which it must have been so employed, and none in which it is necessary to introduce the theologeion. The only known example of the use of the theologeion is that in the Psychostasia. Any further cases in which its presence is assumed must be purely conjectural. Before leaving this subject a few remarks may be made on the general question of the appearances of the gods in tragedy. In the early drama the gods often played an important part in the action of the piece. They came down to earth and mixed with mankind after the old Homeric fashion. Their arrivals and departures might be conducted in a supernatural manner, but when they were once on the stage they moved about like ordinary human beings. Such is still the case in plays like the Eumenides of Aeschylus. But later on, as the tone of the drama became more entirely human, the gods began to be excluded more and more from any real share in the plot. Their occasional presence at the scene of action was managed with more dignity and splendour. It is rare to find them appearing side by side with human beings, as Athene apparently does in the Rhesus and in the opening scene of the Ajax.[657] The Bacchae is an exceptional case, since Dionysus is there disguised as a young man. But usually, in the later drama, the intervention of the gods was restricted to the beginning and the end of the play, when they came forward to speak the prologue and the epilogue. In such cases they no longer join with mortal men in the free and easy intercourse of the Homeric period. Their movements are more dignified and celestial. It is true that in the prologues, when they are alone, and no human beings have yet intruded on the stage, they make their entrance on foot, and walk the earth like ordinary men.[658] But at the end of the play, when the stage is occupied by mortals, they disdain to tread the same ground with them, and are exhibited in the sky by means of the mechane. Even in the prologues it appears that the same practice was introduced in the course of the fourth century, and that henceforth all apparitions of the gods, both at the beginning and the end of a play, were made equally supernatural.[659] This formal introduction of deities at the beginning and the close, which was now practically the sole survivor of the old divine participation in the drama, is the subject of a well-known criticism by Aristotle. He allows that it is perfectly legitimate, when the gods are carefully excluded from the action, and are brought in merely to give information about the past, or to predict the future. But he strongly censures the