For us Athenian tragedy consists of Aeschylus, Sophocles and Euripides. Each was a giant in his own day. And collectively they towered over the theatre of the fifth century. We can see this from a simple fact. In 405 BCE Aristophanes produced a play, Frogs, with a plot based on competition between prominent tragic playwrights. The authors he uses as his two competitors are Aeschylus and Euripides. A third writer is mentioned, Sophocles; he is given far less space than these two, but the play sees him as possessing the same artistic stature as the chosen two. But there are only the three. There is never any question of any fourth tragedian coming into consideration.
So we need not worry that the accident of survival has left us with a body of plays which the Athenians would have regarded as mediocre. But each of the big three competed against, and occasionally lost to, other tragic poets who are now just names but were respected craftsmen in their day. In 415 BCE Euripides’ Alexandros, Palamedes and Trojan Women (with the satyr play Sisyphos) lost to a poet named Xenocles. When Euripides (with his Medea) and Sophocles competed with Aeschylus’ son Euphorion in 431, Euphorion beat both Euripides and Sophocles. These ‘others’ are just names because of a process of generating classics which had begun by the end of the fifth century. Aeschylus died in the 450s; 30 years after his death his status was such that it was formally allowed to produce an old play of Aeschylus at the dramatic festivals instead of a new play written for the occasion. And by the early fourth century it was possible to revive old tragedies by authors other than Aeschylus at the festivals.
Hand in hand with this nostalgia for the theatre of the past went a marked preference for the works of Aeschylus, Sophocles and Euripides. Their works were sufficiently popular not only with festival producers but also troupes of actors who by this time toured the Greek world for the Athenians to become worried about the risk to the texts of the plays. The risk came from the desire of actors to make the most of promising or popular character roles or scenes by adding lines, purple passages or speeches. So the politician Lycurgus arranged for reliable texts to be archived at Athens to protect them against further corruption. Only the trio of Aeschylus, Sophocles and Euripides were singled out for protection in this way, a fair indication that by this stage they were unanimously acknowledged in Athens as ‘classics’, as they had been for Aristophanes three quarters of century earlier.
This taste for the big three was given the final seal of authority at Alexandria in the age after Alexander the great. In the third century BCE a library was founded at Alexandria in Egypt. This library, the most ambitious in the world in its day, became the repository of the great texts of the past. The librarians made strenuous efforts to collect as many texts as they could. In addition, scholars attached to the library worked on the texts, seeking both to reduce the errors which had crept into them through the process of copying by hand and to comment on literary and other matters in the text for the benefit of an intelligent reading public. Their selection of texts for serious study created semi-formal lists of works which (in their view) deserved to be read. The term often given by modern writers to a list of this sort is ‘canon’, though there was no single ancient term. These lists were never intended to limit the opportunities for reading; this was not an attempt at censorship. But the fact that there was a group of texts surrounded by an apparatus of support for the reader will have focused particular attention on the texts which were privileged in this way. The Alexandrian list of tragic poets consisted of Aeschylus, Sophocles and Euripides, the triad of classics recognized already in Athens.
There was another consequence of ‘canonization’. To see this we need scroll forward several centuries; and we need to note two facts. The first is that between the second and the fourth centuries AD there was a major technology transfer. Early books took the form of a continuous papyrus roll, that is a continuous piece of papyrus a metre or more long, on which the text was written in successive columns. As a method of presenting the text this was serviceable enough, as we can see from the fact that it was used for centuries; but it had drawbacks. One drawback was that the roll has to be rewound after reading for the next reader. Another was that (since there were no ‘pages’) reference to specific places in a text was difficult. From the second century, probably under the influence of bible production, this type of book was replaced by the ‘codex’, the name given in antiquity to the book in the form that we know it. This format is more efficient, in that it allows large texts to be compiled (where a roll which has to be rolled and unrolled becomes very clumsy) and it allows easy reference to specific passages in the text. The second fact is that readers in late antiquity were reading a smaller range of authors and texts. Works which come with scholarly support for the reader stood a better chance of making the transfer from roll to codex and therefore continuing to be copied and read. And both of these were vital for survival. The availability of scholarly aids also made certain texts more useful in the schoolroom. Once Christianity replaced paganism as the dominant religion, pagan literature needed to have a visible educational value if it was to be studied, and therefore copied. The content of the text was clearly vital here; but again the cumulative effect of prior privileging would be to give an advantage to those texts for which scholarly support was available.