The key steps that lead to Oedipus' self-knowledge all involve revelations of hidden relationships between himself and Jocasta and Laius -- revelations that prove that the oracle he has spent so many years trying to outrun has caught up with him. Oedipus discovers that he has indeed killed his father (Laius) and married his mother (Jocasta).
- The first step or revelation is that the man whom he has murdered on the road to Thebes was Laius, Jocasta's first husband. At first, the magnitude (that this was also his father) of this isn't clear. But it is step one for Oedipus in discovering the truth about his past. Beginning at line 770, Oedipus delivers a long speech in which he unravels the events that led to his killing Laius.
- Step two is when Oedipus learns from the Messenger that has come to tell him of his adopted father Polybus' death that Polybus was not his natural father. At line 1017, the Messenger says: "Polybus was no kin to you in blood." This cracks the door for Oedipus in realizing that all his attempts to avoid the oracle by running away from the people he assumed were his father and mother were, in fact, completely ineffective in actually avoiding the oracle's prophesy.
- And finally, it is the reuniting of the Messenger from Cornith and a Theban Shepherd that reveals the third and final step to the truth of Oedipus' birth and holds the final key to his self-awareness of the fact that he has murdered not only the king of Thebes (Laius), but his father, and, in turn, married Laius' widow, his mother Jocasta. The Shepherd relays how he gave the baby Oedipus to the Messenger from Corinth, who in turn took the baby to his King, Polybus and his wife to raise as their own. And beginning at line 1182, Oedipus has a brief speech in which everything about his own life becomes clear in a moment. He says:
O, O, O, they will all come,
all come out clearly!. . .
I who first saw the light bred of a match
accursed, and accursed in my living
with them I lived, cursed in my killing.
And so, Oedipus finally has the largest riddle of his life solved when he discovers that he has, in fact, killed his father and married his mother.
Of course, the whole play, in a sense, marks Oedipus's gradual path to self-knowledge as he continues to piece together the evidence about the identity of the murderer of Laius. Interestingly, whilst those who give him that evidence seem to be reluctant to reveal what they know, because they have worked out the identity of the murderer, it takes Oedipus rather longer to accept the final truth.
People will vary in their thoughts about what the three key stages are, but for me, you will want to think about the following parts of the play:
1) The revelation of Teiresias that it was Oedipus who killed his father. Note the way that Oedipus denies this vehemently and cannot accept the truth, thinking that Teiresias is in they pay of Creon - another contender for the throne. Yet this to me is the beginning of the self-doubt that will only end when Oedipus accepts the truth.
2) The re-telling of the murder of Laius by Jocasta in Act II is key because Oedipus, at some level, recognises that it was he who killed Laius. This leads to his calling of the shepherd to give witness and to testify.
3) Lastly, you have to include the poor shepherd in Act IV who finally gives Oedipus the proof that he has long suspected by narrating to him the story of his birth and how he escaped death.