Teiresias is one of a series of characters called upon by Oedipus to reveal information about the person responsible for the cause of the plagues troubling Thebes, and he, like others, is distinguished by a profound reluctance to reveal the information that he has. In his silence, Teiresias forces us to confront the somewhat troubling nature of the truth:
How dreadful knowledge of the truth can be
When there's no help in truth! I knew this well.
But made myself forget. I should not have come.
In a sense, we can admire Teiresias for not wishing to divulge what he knows - as he says, if he did, the knowledge would no longer be his "misery," it would be the "misery" of Oedipus and of Thebes. It is clear that he wishes to be silent to spare Oedipus from the terrible fate of self-knowledge that he knows would completely destroy him and his family. You might want to re-read the speeches of Teiresias in this section of the play to see how he tries to warn Oedipus about the dangers of the truth that he so desperately craves - yet more examples of dramatic irony in this incredible play.
Teiresias, a blind prophet and servant of Apollo, twice was asked by Oedipus to come to the palace to discuss the crisis in Thebes. In the first act of the play he finally appears, revealing the reasons for the city's devastation, knowledge that he is reluctant to reveal to Oedipus for fear of making him miserable. Oedipus, feeling himself to be betrayed by the prophet's resistance, verbally abuses Teiresias ("You sightless, witless, senseless, mad old man!" ) and accuses him of working on behalf of the "usurper" Creon.
Reluctantly, Teiresias tells Oedipus that he should not mock him so quickly; in a famous moment of foreshadowing, he tells the king that it is he who is blind: "But I say that you, with both your eyes, are blind:/You cannot see the wretchedness of your life,/Nor in whose house you live, no, nor with whom." Significantly, Teiresias is also the first character in the play to question Oedipus's assumption that he knows his parentage and to tell him that he has committed atrocities that he does not yet know are his own. He tells Oedipus that he will become blind and poor, that Oedipus is himself Laius's murderer, and that he will learn that he has fathered children with his mother. While Teiresias's presence on stage is brief, as a prophet representing the god Apollo he remains one of the most powerful characters in the play; in addition, the Athenian audience would have recognized him from Homeric mythology (inThe Odyssey the title character must go down into the underworld to gain information from the dead prophet).