It is doubtless one of Aristotle's great services that he conceived so clearly the truth that literature is a thing that grows and has a history. But no writer, certainly no ancient writer, is always vigilant. Sometimes Aristotle analyses his terms, but very often he takes them for granted; and in the latter case, I think, he is sometimes deceived by them. Thus there seem to be cases where he has been affected in his conceptions of fifth-century tragedy by the practice of his own day, when the only living form of drama was the New Comedy. For example, as we have noticed above, true Tragedy had always taken its material from the sacred myths, or heroic sagas, which to the classical Greek constituted history. But the New Comedy was in the habit of inventing its plots. Consequently Aristotle falls into using the word _mythos_ practically in the sense of 'plot', and writing otherwise in a way that is unsuited to the tragedy of the fifth century. He says that tragedy adheres to 'the historical names' for an aesthetic reason, because what has happened is obviously possible and therefore convincing. The real reason was that the drama and the myth were simply two different expressions of the same religious kernel (p. 44). Again, he says of the Chorus (p. 65) that it should be an integral part of the play, which is true; but he also says that it' should be regarded as one of the actors', which shows to what an extent the Chorus in his day was dead and its technique forgotten. He had lost the sense of what the Chorus was in the hands of the great masters, say in the Bacchae or the Eumenides. He mistakes, again, the use of that epiphany of a God which is frequent at the end of the single plays of Euripides, and which seems to have been equally so at the end of the trilogies of Aeschylus. Having lost the living tradition, he sees neither the ritual origin nor the dramatic value of these divine epiphanies. He thinks of the convenient gods and abstractions who sometimes spoke the prologues of the New Comedy, and imagines that the God appears in order to unravel the plot. As a matter of fact, in one play which he often quotes, the _Iphigenia Taurica_, the plot is actually distorted at the very end in order to give an opportunity for the epiphany.(1) (1) See my _Euripides and his Age_, pp. 221-45.