What is the Greeks' view about destiny in light of Oedipus Rex by Sophocles?

The ancient Greeks believed that destiny was determined at birth by the Fates--three sister gods who controlled each person's life and death. Gods ruled over the fate of each Greek, and there was nothing he/she could do to change it. Sophocles portrayed this belief in Oedipus Rex. When the audience reads that Oedipus will kill his father and marry his mother, they are shocked and do not believe that this is possible. Likewise, Oedipus does not believe it because he thinks the parents who raised him ARE indeed his parents. It is not until much later in the story that Oedipus becomes enlightened as to whom his biological parents are. Of course, eventually every one of the Oracle's prophecies come true because Oedipus' fate and the fate of those around him were pre-determined long ago.