How we cite our quotes: (Line)
Quote #4
CHORUS. Zeus, exercising this unlimited control under laws of his own making, is displaying the arrogance of power towards the gods of old.
The Chorus gets right at the problem with Zeus's version of justice: the laws are "of his own making," and maybe not, you know, entirely just. The closing remarks on the "arrogance of power" pretty much convinces us. It starts to sound like Zeus is judge, jury, and executioner, and that he cares more about throwing his weight around than justice.
Quote #5
IO. What crime, son of Cronus, what crime is it you have found me guilty of, that you have yoked me to these sufferings (578-588)
So, Io would really like to know why she's going through all this. Specifically, she asks Zeus what crime she has committed to end up being treated in this way. The fact that Io puts things in this manner suggests that she still sees the world in terms of justice and injustice: if Zeus is punishing her, therefore she must have done something wrong. Is this true? Or is Zeus's "justice" a lot more arbitrary?
Quote #6
IO. Tell me who bound you in this ravine.
PROMETHEUS. The decision of Zeus and the hand of Hephaestus.
IO. And for what wrongdoing are you paying the penalty?
PROMETHEUS. By explaining just so much to you, I have done enough. (617-621)
In other words, Prometheus seems to be denying that he's done anything wrong. All Io needs to know is that Zeus put him here, and that's enough for her to figure out that the punishment is totally arbitrary. Not justice at all.