How we cite our quotes:
(Clytemnestra): "Well, answer me this, without going against your true opinion."
(Agamemnon): "Be sure, I will not falsify my true opinion."
(Clytemnestra): "Would you have vowed to the gods, if you had been in fear, that you would do this thing?"
(Agamemnon): "Yes, if anyone would, with sure knowledge I would have proclaimed this duty." (931-934)
This is a very important passage in the play; unfortunately, it's also pretty hard to understand. Here's the basic gist: Clytemnestra is trying to get Agamemnon to walk on the purple fabrics. Then she says, "Oh come on, you're telling me that, if you were ever in a really bad situation, and the only way to get out of it was by swearing to step on purple fabrics, you wouldn't swear to do it?" Then Agamemnon says, "Of course I would." What Agamemnon doesn't seem to notice is that he never is or was in that sort of situation, and he never swore to step on the fabrics, so he doesn't have to now. Oh well.
But that's not the point of why we're quoting this passage here. What's important in the context of the theme of "Fear" is that Clytemnestra's words show that she recognizes that fear will make people do anything. If so, it is surprising that she doesn't realize that it was also Agamemnon's fear that made him sacrifice his daughter Iphigenia; actually, the situation he found himself in then is almost the exact parallel of the one Clytemnestra describes, if you replace stepping on fabrics with killing your daughter. Why doesn't she understand this? Or do you think she does understand, but just doesn't care?
(Clytemnestra): "And what do you think Priam would have done, if he had achieved what you have?"
(Agamemnon): "I think, he would have certainly walked on embroideries."
(Clytemnestra): "Then have no regard for men's censure."
(Agamemnon): "But the people talk; there voice is very powerful."
Like Aegisthus, Agamemnon is afraid of what the people will think about him. But you might also say that he is afraid of people thinking that Priam, the king of Troy, is better than him. This is why Clytemnestra is able to peer pressure Agamemnon into walking on the fabrics by convincing him that Priam would have done the same, if he'd had the chance.
(Chorus): "Why, why is this terror
in front of my heart, to rule its divinations?
and why does my song act the seer, unbidden,
unpaid? and why is confidence
not enthroned at my mind's own seat,
easily persuading me to spurn my terror
like a doubtful dream?" (975-983)
Here, the Chorus provides a vivid description of fear and confusion. Their fear seems to be heightened by the fact that they don't know why they are afraid.