The conflict between James and Mary Tyrone is one that occupies the whole play and is used by O'Neill as a vehicle for revealing the past history of this particularly troubled family. At the beginning of the play, the audience is presented with the Tyrones and clearly Jmes Tyrone tries to present an optimistic view of their relationship. Clearly he hopes that Mary has conquered her addiction to morphine and she is on the road to recovery. The play of course charts the downward path of this hope, as James Tyrone is forced to admit that unfortunately his wife is still just as addicted to morphine as she ever was, as she herself acknowledges in Act II scene 2, when she says to her husband:
I don't blame you. How could you believe me--when I can't believe myself? I've become such a liar. I never lied about anything once upon a time. Now I have to lie, especially to myself. But how can you understand, when I don't myself. I've never understood anything about it, except that one day long ago I found I could no longer call my soul my own.
Mary's quote is significant in this section of the play because it captures the way that deceit and lies capture so many of the relationships between the family. After all, Mary may be addicted to morphine, but her husband never really faces up to his alcoholism and various other issues he has. Following this moment, the conflict between Mary and James is one that causes Mary to become more and more withdrawn as she retreats into morphine-inspired reveries of the past and James is forced to accept her decline in health.