Explain the flaw in Oedipus's thinking in the story he relates in lines 934-959 in Oedipus Rex by Sophocles. What is the relevance and significance of the evidence the messenger gives in the dialogue contained in lines 1225-1239?
The story Oedipus relates about his experience with the oracle's prophecy in Oedipus Rex by Sophocles does, as you suggest, have a few flaws.
Oedipus explains that he was perfectly content with his life as the son of the King and Queen of Corinth until one night a man drunk on wine claimed Oedipus was not really the son of Polybos and Merope, the king and queen. Of course this would be upsetting to hear, but for a day or so Oedipus just thinks about what the man said, though of course he wants to do something to find out the truth.
The next day he does ask his parents about the man's claim, and they were furious that this man had insulted them by suggesting such a thing. This reassures Oedipus a bit,
the accusation always troubled me—
the story had become well known all over.
It is clear that the drunk man is not the only one who believes that Oedipus is not the birth son of Polybos and Merope, and Oedipus is troubled enough about this matter that he sneaks off to see the oracle at Delphi, hoping to find out the truth about his parentage. Unfortunately, Oedipus says that
Apollo sent me back without an answer,
so I didn’t learn what I had come to find.
He does not learn the truth about his parents, but what Apollo does tell him is so horrible that Oedipus did not even want to think about it. The "monstrous things" which Apollo says include two abominable things. First, Apollo says that Oedipus will "defile" his mother's bed, which of course means he will have sexual relations with her. Even worse, the two of them will
...bring forth to men a human family
that people could not bear to look upon....
Second, Apollo tells Oedipus that he will murder "the father who engendered" him. When he hears these things, Oedipus runs away immediately, never even returning to Corinth to say his goodbyes,
so I would never see that prophecy fulfilled,
the abomination of my evil fate.
The flaw in Oedipus's thinking is simple: he came to Delphi to get the truth, but when he hears it he rejects it. Why seek the gods for truth if you are not going to listen to anything they say? It is certainly a demonstration of faulty reasoning, and it is the first time he tries to circumvent the gods. His reasoning is also flawed in this regard: if he feels strongly that Polybos and Merope are not his parents (which is why he came to Delphi), he should not be afraid to go back to Corinth because they are not his parents from birth. It is certainly a confusing time for the young man.
The conversation between Oedipus and the messenger is quite telling. The man was a shepherd on the mountain when a man gave him a baby, the baby we now know was Oedipus. Here's what we know, then. Somebody put a spike through his or her son's ankles and gave him to a messenger. The messenger was obviously supposed to take the boy away, and he does. He gave the boy to a shepherd, and of course we know the shepherd did not keep the boy. He had to have given him away, right? Oedipus is a riddle-solver, and he is beginning to see that he may have killed Laius on the mountain.