In Antigone, why does Sophocles open with the dialogue between sisters?
This is an interesting move on Sophocles' part, as women were clearly considered inferior creatures in his time (and in the time he wrote about). (It may not be relevant here, but consider that all actors were men, as well--so the two women in question were, in fact, men.)
Creon has passed a decree that only Eteocles, having fought on the side of Thebes, is to be given proper rites and burial, but Polyneices--his brother, who fought against Thebes--was to have the ultimate dishonor of being left unburied and dishonored, as carrion for birds. Later in the play, when Creon is confronted about this--by Antigone and by Haemon at separate times--he refuses to be "ruled by women." How, he argues, can a woman know better than a man? He refuses to listen to anyone who sides with Antigone, because she openly defied his decree (and he feels that, as a ruler, he cannot let that pass, even though she is betrothed to his son Haemon and the daughter of the late ruler of Thebes, Oedipus), but mostly, it seems, he will not listen because she is a woman.
But Sophocles opens the play where we are forced to listen to women. As they lay out the situation and discuss their plans, we find ourselves on Antigone's side. It's part of the glory of literature that audiences can be drawn into sympathy with those they normally would not give the time of day to by such subtle devices.