Recently our Greek group finished reading Oedipus at Colonus, the last, posthumously produced, play of the tragedian Sophocles of Colonus (this is the famous Sophocles, but the specification is relevant here). The 'trilogy' of Theban plays known today is not a true trilogy, but rather three individual plays from three trilogies from a tragedian who has a deep attachment to the Theban Cycle. Not only are these plays separate, but it is impossible to tell for certain where they fit into the cycles of their respective trilogies.
One may, nonetheless, form opinions about such matters. It seems likely that the Oedipus at Colonus is the last of its trilogy. The correspondence of the agedness of the protagonist and the playwright, who fittingly did not live to see the premier performance, is one piece of evidence. The Oedipus at Colonus is also heavy on the talking, even for a Greek tragedy. The choice of protagonist and setting, in the Grove of the Kindly Ones forces the other characters to come to Oedipus rather than mingling freely. Each of Oedipus' male relatives come to him as petitioners as if he were already apotheosized. Oedipus fills the prophetic role usually reserved for Tiresias in Theban material. Oedipus undergoes apotheosis at the end, thereby removing himself from any following plays - this apotheosis prompted one of our group to describe the Oedipus at Colonus as the anti-Iliad, since Achilles' arc in that work involves his realization that, no matter how mighty he is, no matter his lineage, he is nonetheless mortal. Oedipus, in contrast, becomes more and more aloof from mortal concerns as the Oedipus at Colonus continues, culminating in his ascent in status to a hero cult, the level accorded to those below the falling angel and above the rising ape. The details surrounding this apotheosis are not always clear in their symbolism, but this is to be expected of a ritual which ends a play that frequently enjoins reverent silence.
One could argue that the many speeches of Theban partisans in the Oedipus at Colonus are a way of setting up the conflicts and this is therefore the first of its trilogy. In that case, the shadow of the Colonus would hang over the participants in the coming war. This is less likely than the above for two reasons. The first is that Sophocles had already written the angry aftermath of conflict in Antigone, the earliest of his extant Theban plays. The more mature approach of Oedipus Tyrannus, the chronologically middle play, suggests that Sophocles, as playwright, was writing the plays according to his aging and increase in understanding rather than the internal chronological order of the Theban Cycle. The last trilogy, therefore, would focus on the last days of Oedipus just as Sophocles is declining, although perhaps not as much as his sons and heirs might wish. The second reason is that Sophocles is a Colonus lad himself, possessing a great interest in the cycle around the hero. The other two surviving plays are set at Thebes, but the shrine is at Colonus. The playwright's last work should end where he began.
