The ancient Greeks believed that their gods could see the future, and that certain people could access this information. Prophets or seers, like blind Tiresias, saw visions of things to come. Oracles, priests who resided at the temples of gods—such as the oracle to Apollo at Delphi—were also believed to be able to interpret the gods' visions and give prophecies to people who sought to know the future. During the fifth century B.C.E., however, when Sophocles was writing his plays, intellectuals within Athenian society had begun to question the legitimacy of the oracles and of the traditional gods. Some of this tension is plain to see in Oedipus Rex, which hinges on two prophecies. The first is the prophecy received by King Laius of Thebes that he would have a son by Queen Jocasta who would grow up to kill his own father. The second is the prophecy that Oedipus received that he would kill his father and marry his mother. Laius, Jocasta, and Oedipus all work to prevent the prophecies from coming to pass, but their efforts to thwart the prophecies are what actually bring the prophecies to completion.
This raises a question at the heart of the play: does Oedipus have any choice in the matter? He ends up killing his father and marrying his mother without knowing it—in fact, when he is trying to avoid doing these very things. Does he have free will—the ability to choose his own path—or is everything in life predetermined? Jocasta argues that the oracles are a sham because she thinks the prediction that her son would kill her husband never came to pass. When she finds out otherwise, she kills herself. In Oedipus Rex, Oedipus has fulfilled his terrible prophecy long ago, but without knowing it. He has already fallen into his fate. One could argue that he does have free will, however, in his decision to pursue the facts about his past, despite many suggestions that he let it go. In this argument, Oedipus's destruction comes not from his deeds themselves but from his persistent efforts to learn the truth, through which he reveals the true nature of those terrible deeds. Oedipus himself makes a different argument at the end of the play, when he says that his terrible deeds were fated, but that it was he alone who chose to blind himself. Here, Oedipus is arguing that while it is impossible to avoid one's fate, how you respond to your fate is a matter of free will.
The play begins with a declaration from the oracle at Delphi: Thebes is suffering because the person guilty of the murder of King Laius has not been brought to justice. Oedipus sets himself the task of discovering the guilty party—so guilt, in the legal sense, is central to Oedipus Rex. Yet ultimately it is not legal guilt but the emotion of guilt, of remorse for having done something terrible, that drives the play.
After all, one can argue that neither Oedipus nor Jocasta are guilty in a legal sense. They committed their acts unknowingly. Yet their overwhelming feelings of guilt and shame for violating two of the basic rules of civilized humanity—the taboos against incest and killing one's parents—are enough to make Jocasta commit suicide and to make Oedipus blind himself violently.
When Oedipus publicly declares his intention to solve the mystery of King Laius's murder, he says, "I'll start again—I'll bring it all to light myself." Oedipus's vision and intelligence have made him a great king of Thebes—he solved the riddle of the Sphinx and revitalized the city. But he is blind to the truth about his own life. It takes the blind prophet, Tiresias, to point out his ignorance and to plant the first seeds of doubt in Oedipus's mind. When Oedipus mocks Tiresias's blindness, Tiresias predicts that Oedipus himself will soon be blind. And indeed, when Oedipus learns the full story—that he has killed his father and married his mother—he gouges out his eyes. He learns the nature of fate and the power of the gods, but at a great cost. And though he is blinded, he has learned to see something he could not see before.
The terrible deeds that are Oedipus's undoing actually took place long before the play begins. King Laius has been dead for many years, Oedipus has ruled for some time, and his marriage to Jocasta has produced four children. They might have all remained happy in their ignorance had the plague not come to Thebes and the oracle not commanded that the murderer of Laius be found. Good king that he is, Oedipus swears he will find the murderer. Every step of the way, people are reluctant to speak and try to tell him that it would be better if the past were left alone. Creon suggests that they discuss the oracle behind closed doors, not in front of everyone, but Oedipus wants to show that he is open to the truth and keeps no secrets from his people. Tiresias refuses to say what he knows, and only speaks when he has been insulted and accused of treachery. Jocasta begs Oedipus to cease his investigations. The old shepherd gives Oedipus the final pieces of the puzzle only when threatened with death. In his desire to seek out the truth and save his people from the plague, Oedipus becomes his own prosecutor, and then his own judge and punisher.
In his quest for truth, Oedipus is a man of constant action. When the priests come to ask for his help, he has already dispatched Creon to the oracle to find out what the gods suggest. When the chorus suggests that he consult Tiresias, Oedipus has already sent for him. Oedipus decides quickly and acts quickly—traits his audience would have seen as admirable and in the best tradition of Athenian leadership. But Oedipus's tendency to decide and act quickly also leads him down a path to his own destruction. He becomes convinced that Tiresias and Creon are plotting to overthrow him, though he has no evidence to prove it.
At several stages where he might have paused to reflect on the outcome of his actions—where he might have sifted through the evidence before him and decided not to pursue the question further, or not in such a public way—he forges onward, even threatening to torture the reluctant shepherd to make him speak. And it is the shepherds words that irrefutably condemn Oedipus. Even here, his will to act doesn't end. Discovering Jocasta, his wife and mother, dead, Oedipus quickly takes his punishment into his own hands and gauges out his eyes.