What is the background surrounding this quote, and what is the meaning of this quote? “Cast out an honest friend, and you cast out your very life—your dearest treasure.”
Oedipus misguidedly accuses the blind prophet, Teiresias, as well as his own brother-in-law, Creon, of conspiring against him to take his throne. He grows angry when Teiresias refuses to tell him what he knows about Laius's murderer and Oedipus's own background. Although Teiresias is actually trying to protect Oedipus because he knows that the truth will destroy him personally and politically, Oedipus is too short-fused and short-sighted to accept this. Oedipus insults the prophet cruelly and jumps to conclusions for which he really has no evidence; his rash and impulsive judgment leads, in part, to his downfall.
Creon, the queen's brother, is quite a rational man, neither as impulsive nor as rash as Oedipus is, and he tries to talk sense into Oedipus when he returns to the palace. Creon has always tried to support Oedipus, and he therefore enjoys a great deal of power, without as much responsibility as the king must bear. He speaks the words that you've cited, as he attempts to convince Oedipus that Oedipus is making a mistake by alienating those people who have only tried to help him. He means that, by estranging a good and loyal friend, a person harms themselves and their own lives. Such friends, who are loyal as Creon is, are hard to come by, especially for kings (who might be surrounded by people who flatter them in order to curry favor). Sadly, Oedipus doesn't listen.
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