Clytemnestra was driven by her jealousy toward her husband's concubine, Cassandra, and by her desire for her own lover, Aegisthus. Clytemnestra says "Do not blame me, I was in the hand of Fate" yet her claim that it was the general curse on the house of Atreus that caused her to act as she did is untenable (135). Thus the essential responsibility for the acts that start the chain of consequences addressed in the Choephori seems to rest with the free human actors--Clytemnestra and Aegisthus. They were under no compulsion to kill the king since avenging Iphigenia's death was not--given the circumstances--a compelling reason to do so and their crime was, therefore, murder.
But their crime was also an assassination and Orestes, by virtue of his birth, believes himself compelled to avenge his father. The murder upset the political situation in Argos and Aegisthus's assumption of the throne was illegitimate and needed to be corrected in and of itself. Since Aegisthus and Clytemnestra were also tyrants the social order was doubly disrupted and allowing their crime to go unpunished meant acceding to this state of affairs. Failure to avenge Agamemnon, therefore, meant failing to defend justice in the political sphere. The 'world', therefore, demands this action. The actor is not free in the sense that if he wishes to be just he must act justly in ridding Argos of the tyrant. Since Orestes is also the only person who can leg