Oedipus Denies the Truth
Effects: On the Audience
Allows plot to thicken and makes catharsis for audience even greater.
Dramatic irony as the original Greek audience (and modern one) know Oedipus' back-story, so to some extent some enjoyment, but eventually getting bored and fed up. (Especially as this is the main and recurrent action in the play.)
We learn more about the characters/characterisation. Eg Oedipus is keen to seek proof and evidence for himself, is unbending towards Creon and is stubbornly holding on to the glimmer of hope that he is not responsible for his father's death (and the rest of the prophecy coming true). And Jocasta is initially impious with regard to prophecies and gods' powers.
Tension is heightened and diminished several times in the play (in anticipation of Oedipus' own reaction) so the audience feels pity and fear leading to catharsis.
Audience can relate to not wanting to confront the worst aspects of their own lives or actions. ('what would you do?')
Opportunity to think deep questions like 'to what extent is Oedipus' eventual outcome due to fate or his own (fateful?) actions...'
On the Other Characters
Creon is accused of treason and plotting against the king, and therefore Thebes, as Oedipus does not believe Tiresias' terrible messages.
Tiresias is forced to fight back verbally to defend his position and skills. He is also forced to reveal the truth to Oedipus.
Jocasta reinforces her opinion that prophecies are false. Her hanging gets delayed till the point where both realise the truth (fifth episode).
The Corinthian messenger feels obliged (and believes he will a receive a reward) to tell Oedipus that he was not Polybus and Merope's natural son.
On the Plot
Oedipus disputes with Creon the truth/falsity of Tiresias' prophecies. He is insistent that Tiresias is not speaking the truth and so Creon must therefore be using him to diminish Oedipus' reputation and elevate himself.
Jocasta reveals her information to Oedipus and he tells her the prophecy conferred to him by the oracle at Delphi. She does not know the full story and is possibly trying to deny the credibility of her prophecy.
The search for the shepherd who witnessed the murder of Laius (as well as saving Oedipus from his death) is initiated. Oedipus hopes, against hope, that the tiny detail of 'thieves' vs 'one man' holds true, and so that his hands are clean of Laius' blood.
Oedipus' (and Jocasta's) agony at finally discovering the truth is heightened and made even more horrific and sufferable and hurting. They have delayed the moment of truth long enough and face the immense shock and fall from grace.
Causes
He jumps to his own conclusions, and does not take into accont the information being providing to him
He is unaware of the true situation regarding his parents and genuinely believes he is right; lack of full information
He thinks that Tiresias is providing him false and outrageous information and that he has been "primed" by Creon
The truth is too much to handle to much to contemplate/live with - it is such a horrible suggestion that Oedipus does not want to think about or believe it
Self-preservation, brought curse down upon himself but wants to believe otherwise
Jocasta discredits the prophecies and convinces him to believe in their falsity
Personality, lack of full info, Jocasta and outrageousness
Oedipus has a stubborn personality and does not change his mind easily or quickly
On Oedipus himself
His denial of the truth leads him to get hot-headed towards Tiresias and cold with Creon, regarding him with great suspicion.
His denial of the truth allows Oedipus to discover the real truth about who his parents actually are, and as a consequence, the horrific and unspeakable travesties he has committed.
His denial of the truth makes his own sharp fall from grace even more dramatic and terrifying, and this is reflected in his vicious eye stabbing.
His denial of the prophecy from the oracle makes him focus on his glory from the defeat of the sphinx, as opposed to the circumstances of the previous king's death (which he wouldn't really have cared too much about, until this food crisis/plague).