In the ancient Greek tragedy Oedipus Rex, written by Sophocles in about 440 BC, Oedipus's ignorance of the circumstances of his life don't lead directly to his blindness to the truth. His blindness to the truth is his purposeful refusal to believe the truth, even after it's been revealed to him.
In his Poetics, Aristotle wrote that the best Greek tragedies—of which he considered Oedipus Rex the best example—proceed in a logical cause-and-effect manner. In Oedipus Rex, the revelation of one truth leads to the revelation of another truth until all truths are revealed and the play comes to its logical and, for Oedipus, inevitably tragic end.
Oedipus Rex begins, as most classic Greek tragedies do, in the midst of a crisis. The people of Thebes are suffering from a drought and a plague, and they appeal to Oedipus, King of Thebes, to relieve them of their suffering.
The Oracle at Delphi reveals that in order for the famine and pestilence to end, Thebans must find and banish the person who murdered their former king, Laius.
Oedipus, unmindful of his role in the death of Laius, vows to find the murderer and banish him from Thebes.
Thus far, Oedipus's ignorance of the facts of Laius's death is of little consequence, and doesn't negatively impact his life. His vow to the people of Thebes is honest, straightforward, and heartfelt, and he intends to fulfill it.
As the plot unfolds, however, it becomes increasingly clear that Oedipus himself is the murderer, and how he reacts to that information will result in his tragic fall.
Oedipus sends for the blind seer-prophet Teiresias, who is at first reluctant to tell Oedipus what he knows about the murder. Oedipus insults Teiresias for his refusal to speak to the matter and accuses Teiresias of the murder. Teiresias angrily responds that Oedipus is the murderer.
Oedipus refuses to believe Teiresias and accuses him of conspiring with Creon, Oedipus's brother-in-law, to usurp his throne. As Teiresias leaves the palace, he reveals an old prophecy that Oedipus would kill his father and marry his mother.
Oedipus has now heard two truths, both of which he refuses to believe, but, as yet, these truth have no real consequence on his life.
Oedipus confronts Creon, accusing Creon of telling Teiresias what to say so Creon can usurp his throne. As Oedipus and Creon argue, Jocasta, Oedipus's wife and Queen, emerges from the palace. She recounts the circumstances of Laius's murder, which are remarkably similar to Oedipus's own recollection of killing a man on the road to Thebes.
Even as circumstantial evidence mounts against him, Oedipus refuses to believe that he's the murderer, and he continues his investigation, still ignorant of the truth and convinced that he will be vindicated.
This is when Oedipus's tragic flaw, his hubris, comes into play. His pride affects two different but inextricably interrelated circumstances.
The first circumstance is that Oedipus must prove that he has fulfilled his vow to the Theban people and discovered the murderer.
The second circumstance, which is a matter of maintaining his power and authority in Thebes and which is tragically in conflict with the first circumstance, is to prove that he's not the murderer.
Out of selfish pride, Oedipus chooses self-preservation rather than the good of the people. Under the guise of fulfilling his vow to find the murderer, he chooses instead to focus his efforts on proving that he's not the murderer.
Oedipus is no longer ignorant of the facts, but to accomplish his goal of proving himself innocent of the murder, he blinds himself to the truth of Laius's murder, hoping that the Theban people will also be blinded to the facts.
Ultimately, despite Oedipus's efforts, all of the facts become known, and Oedipus fails in his efforts to prove himself innocent of the murder.
The irony is that by choosing to focus his efforts on proving that he's not the murderer, Oedipus fulfills his vow. He finds, and banishes, Laius's murderer. Through his pride, which led to his tragic fall, Oedipus relieves the suffering of the Theban people.