Oedipus's actions at the beginning of they play prove him to be a very naive and arrogant person. We especially see evidence of his naivete in his conversation with Tiresias. Frequently, Tiresias refers to Oedipus as the one who is actually blind, which is ironically the truth. As Tiresias states, it is actually Oedipus's deeds, unknown to him, that have angered the gods and are causing Thebes' current, devastating plague. Tiresias accuses Oedipus of being blind to his own actions in the lines:
I will reply, since you reproach me as blind: You, even though you see clearly, do not see the scope of your evil, nor where you live, nor with whom you dwell. (432-435)
Being blind in this context is akin to being naive, showing us that Oedipus's actions in the beginning of the play are guided by naivete.
We also see evidence of Oedipus's arrogance in the beginning of the play. His arrogance leads him to draw the conclusion that Creon is engaging in a plot to try and overthrow Oedipus. In fact, Oedipus even accuses Tiresias of being involved in the plot, which is why he becomes so angered by Tiresias's prophecy and will not give it credence. We see Oedipus accusing Creon and Tiresias of plotting his overthrow in the lines:
... the trusted Creon, my friend from the beginning, beguiles me and secretly desires to oust me, engaging this craftily-working wizard, this tricky beggar, who sees clearly only for profit. (405-409)
Oedipus is of course referring to Tiresias as the "craftily-working wizard" and accusing him of accepting payment from Creon to help overthrow Oedipus with false prophecy.
However, by the end of the play Oedipus's thirst for the truth and his desire to end the plague turn him into a humbled and agonized man. He can no longer deny the truth of what Tiresias says once he learns from Jocasta that King Laius was killed at a crossroads heading towards Delphi, nor can he deny the prophecy once he learns from the Shepherd that he gave away Jocasta's baby. The knowledge that he is the one who has caused the plague and committed atrocious sins against his parents and the gods humbles him, makes him gouge out his own eyes, and also leads him to step down as king and leave the city. The fact that he can humble himself shows that he actually is a man of strong and noble character.