Oedipal Foundations

A fundamental basis for all of Freudian psychology resides in the Oedipal feelings which Freud believed were common to all men. The major psychological distinction between one person and another was said to come from the way the person handled those feelings and the way that handling was represented in every day life. Freud is categorical about the existence of the Oedipal impuls

It is the fate of all of us, perhaps, to direct our first sexual impulse towards our mother and our first hatred and our first murderous wish against our father. Our dreams convince us that that is so. King Oedipus, who slew his father Laïus and married his mother Jocasta, merely shows us the fulfillment of our own childhood wishes...

Here is one in whom these primeval wishes of our childhood have been fulfilled.
While the poet, as he unravels the past, brings to light the guilt of Oedipus, he is at the same time compelling us to recognize our own inner minds, in which those same impulses, though suppressed, are still to be found.  - Sigmund Freud, The Interpretation of Dreams, tr. James Strachey, Avon, N.Y. 1965. p.296.

He finds it's expression just as categorical in Oedipus Rex.

"Oedipus and the Sphinx"
Gustave Moreau

At a point where Oedipus, though he is not yet enlightened, has begun to feel troubled by his recollection of the oracle, Jocasta consoles him by referring to a dream which many people dream, though, as she thinks, it has no meaning:
     Many a man ere now in dreams hath lain
     With her who bare him. He hath least annoy
     Who with such omens troubleth not his mind.
Today, just as then, many men dream of having sexual relations with their mothers, and speak of the fact with indignation and astonishment. It is clearly the key to the tragedy and the complement to the dream of the dreamer's father being dead.  - Sigmund Freud, The Interpretation of Dreams, tr. James Strachey, Avon, N.Y. 1965. p.297.

It is clear that an innate desire to kill one's father and sleep with one's mother runs contrary to the very fabric of our society. For orthodox Freudian thinkers, the difference between this innate urge and the demands of our civilization is mediated by repression and sublimation. Either the inappropriate urges are repressed (which risks manifesting itself in psychological illness) or they are transformed into some expression which is useful to society.