What does Sophocles intend to prove and illustrate in Oedipus Rex?

We can argue that the
central theme of this
play is man's ignorance and his subordinate relationship to the gods. The

story of the play clearly illustrates the folly of man's attempts to overcome the will
of the
gods. 

The idea is articulated directly in the
dialogue as well, as we see
here in these lines from :

JOCASTA: 
Why should a
person fear
when the ways of fortune 
are supreme, when there is no clear
foresight?
(1005) 
Its best to live at random, however one
can.

Theof' fate is that he is born
into a situation that dooms him (via prophecy) to live
out
a...