Tragic irony was used initially in ancient Greek tragedy and later almost in all tragedies. Irony consists essentially in the contrast of the two aspects of the same remark or situation. A remark made by a character in a play may have one meaning for him and another meaning for other character and the audience or one meaning for the speaker and the other characters and another meaning for the audience. Similarly, a situation may have a double significance in the sense that a disaster may be foreseen by the audience while the characters may be ignorant of it. Irony heightens the tragic effect. Sophocles has used irony with striking effect in his plays.
"Oedipus Rex" is replete with tragic irony and is found in most of the speeches and situations. There are many occasions on which the audience is aware of the facts while the speaker is ignorant of those facts and some other characters, on the other hand, present a contrast which lends an increased emphasis to a tragic fact or to the ultimate tragic outcome. The proclamation of Oedipus that he will make a determined effort to trace the murderer of Laius and the curse that Oedipus utters upon the killer and upon those sheltering the criminal, possess a tragic irony in view of the audience's knowledge that Oedipus himself will ultimately prove to be Laius' murderer. Oedipus proclaims that no house in Thebes is to provide shelter to the guilty man and that the gods will curse those who disobey his command. Thus, without knowing the real meaning of his words, Oedipus announces the sentences of banishment against the murderer and heightens the tragic effect of the discovery which comes towards the end of the play. Oedipus does not know that he himself is to become the victim of the punishment which he is proclaiming but the audience knows it. In this contrast between Oedipus' ignorance and our knowledge of the true fact lies the tragic irony.
The scene between Oedipus and Teiresias is fraught with tragic irony throughout. Teiresias is the prophet who knows everything while Oedipus does not know himself as such. Teiresias would not like to disclose the secret but Oedipus quickly loses his temper thus provoking the prophet to say what he never wanted to say. Teiresias tells Oedipus that he himself is the guilty man he is seeking and that he is living in a sinful union with the one he loves. The impact of these words is totally lost upon Oedipus. The charges of Teiresias enrage him and he insults the prophet by calling him a sightless sot showing his own inner blindness. An irony lies in the fact that Teiresias, physically blind, knows the truth while Oedipus, having normal eyesight, is totally blind to that truth. There is irony also in the contrast between what Oedipus truly is and what he thinks himself to be. To Teiresias he boasts of his intelligence citing his past victory over the Sphinx. The terrible predictions that Teiresias makes regarding the fate in store for Oedipus also possess irony in the sense that, while we know their tragic imports, Oedipus treats them as the ravings of a madman. These predictions become more awful when we realize that they will prove to be true and valid. Teiresias warns Oedipus that the killer of Laius will ultimately find himself blind, an exile, a beggar, a brother and a father at a same time to the children he loves, a son and a husband to the woman who bore him, a father-killer and father-supplenter. Even the Chorus, ignorant of the facts, refuses to believe what Teiresias has said about Oedipus. Thus both Oedipus and the Chorus are unaware of the truth while Teiresias and the audience is fully aware of it.
Tragic irony is also found in the scene with Creon. Creon begs Oedipus not to think him a traitor and not to pass the sentence of death or exile against him. But Oedipus blinded by his authority and his anger shows himself relentless. This situation is ironical of the final scene where the roles are reversed. There Oedipus begs Creon to look after his daughters, and entreats him to pass the order of banishment against him. Creon, being a moderate man, does not show himself unrelenting in that scene. The pathos of the final scene is intensified.
Then there is the scene with Jocasta. Oedipus and Jocasta are ignorant of the true facts. The audience, aware of the facts, experiences a deep sorrow at the fate which is going to overtake these characters. Jocasta is sceptical of oracles. She thinks no man possesses the secret of divination and as a proof she tells what she and her husband did to the child, who, according to the oracle, was to kill his father. There is palpable irony in Jocasta's unbelief in oracles and her citing as proof the very case which is to prove the truth of one oracle received by her and the late Laius. This irony deepens Jocasta's tragedy.
There is irony also in the account of his life which Oedipus gives to Jocasta. Oedipus thinks himself to be the son of Polybus and Merope: he fled from Corinth after the oracle had told him of the crimes he would commit: he has all along been under the impression that he has avoided committing the crimes foretold by the oracles. But all the time Oedipus has been unknowingly performing certain actions leading to the fulfillment of those very prophecies which he had been striving to belie, just as King Laius had earlier taken desperate but futile measures to prevent the fulfillment of the prophecy which has been communicated to him by the oracle.
When the Corinthian messenger brings the news of Polybus' death, Jocasta gets another chance to mock at the oracles without realizing that her mockery will turn against herself.
"Where are you now, divine prognostication?"
Jocasta tells Oedipus that this news proves the hollowness of oracles because Polybus whom Oedipus believed to be his father has died a natural death. There is irony also in the simple remark of the messenger that Jocasta is the "true consort" of a man like Oedipus. Neither the messenger nor Jocasta knows the awful meaning of these words. Jocasta makes an exultant speech on the desirability of living at random and on mother marrying as merely a figment of the imagination. Jocasta makes this speech only a few moments before the truth dawns upon her. The Corinthian, who wanted to free Oedipus of his fear of marrying his mother, ends by revealing, unknowingly, the fact that Jocasta's husband, Oedipus, is really her son, although this revelation is at this stage confined to Jocasta. The tragic irony of this situation and in what is said by the Corinthian and Jocasta in this scene is evident.
The song of the Chorus, after Jocasta has left in a fit of grief and sorrow, is full of tragic irony. The Chorus thereby pays a tribute to what it thinks to be the divine parentage of Oedipus. There is a big contrast between this supposition of the Chorus and the actual reality. The arrival of the Theban shepherd is the point at which the climax of the tragedy is reached.
After the discovery there is hardly any room for tragic irony. The concluding part consists of a long account of the self-murder and the self-blinding, a dialogue between Oedipus and the Chorus, and a scene between Oedipus and Creon including the brief lament by Oedipus on the wretched condition of his daughters. The concluding portion of the play is deeply moving and poignant, but contains little or no tragic irony.
Oedipus Rex bristles with tragic irony. It opposes Oedipus against those who know i.e. Teiresias. Where characters themselves are not omniscient, the audience is. The audience knows the gist of the story and can be surprised only in the means by which the necessary ends are achieved. They know that Oedipus is, in all sincerity, telling a falsehood when he says:
"I shall speak, as a stranger to the whole question and stranger to the action."
The falsehood is, however, qualified in the term stranger: the stranger who met and killed King Laius, who met and married Queen Jocasta, the stranger who was no true stranger at all. At the outset, he says:
"For I know well that all of you are sick, but though you are sick, there's none of you who is so sick as I."
Here he is, indeed, speaking the truth, but more truth, than he knows, because he is using sickness only in a symbolic sense while actually it is true of him in a literal tense.
In addition to this irony of detail, there is a larger irony in the inversion of the whole action. The homeless wanderer by delivering the city of Thebes from the sphinx and marrying Jocasta became a King in fact, but this revelation turned him once more into a homeless wanderer, who had once gone bright eyed with his strong traveller's staff, now uses the staff to feel the way before him.
The reversed pattern is seen again in the fact that the cruel oracles have their darkest moment just before they come clear. Jocasta's words mocking the prophecy of the gods are echoed and amplified in Oedipus' typical tyrant-speech of unbelief. The role of the helpers is another example. Sophocles provides at least one helper, or rescuer, for every act. The appeal in the prologue is to Oedipus, himself a rescuer in the past. Oedipus appeals to Creon who comes from and represents Apollo and Delphi. It is as a rescuer that Teiresias is called. Jocasta intervenes to help. So does the Corinthian messenger, and the last helper, the Theban shepherd, is the true and original rescuer. Those who do not know the reality are eager to help; those who know are reluctant. But all helper alike push Oedipus over the edge into disaster.