Belief in Greek philosophy is the belief that someone's fate is pre-determined and unchangeable. The Greeks believed that fate should be accepted because it ultimately cannot be avoided.
In the Greek tragedy, Oedipus the King, the irony of fate brings the downfall of Oedipus. Fate, in this story affects three specific characters. The gods have already decreed Oedipus and Jocasta’s fate even before they know it. Their fate was in fact decreed the day they were born, and trying to avoid seems to have been pointless.
Oedipus unsuccessfully tries to change his fate. An oracle has confirmed that his destiny is to marry his mother and kill his father. He does everything he can to change that fate, but because of his parents' actions in ordering him killed as an infant; his knowledge of the people who've raised him as parents is incorrect. All in all, he had no say in his fate and was incapable of changing anything. Thus, we have our tragedy.
Source(s): Oedipus Rex