By the end of act 2 in The Crucible, John Proctor has become extremely concerned about the rampant accusations of witchcraft that are leading to the conviction and killing of many people in Salem. He understands that personal rivalries unrelated to witchcraft are motivating many people. In particular, he realizes that Abigail Williams is spreading lies specifically to harm him and his wife, Elizabeth. Abigail never forgave him for rejecting her. The situation becomes critical when Elizabeth is arrested. As John pushes Mary Warren to tell what she knows, it is clear that Mary’s fear of Abigail far outweighs her confidence in the justice system. John’s concern becomes urgent after Elizabeth is arrested, for she probably faces a death sentence if convicted.
In act 3, John takes Mary to the court and speaks with the judges. Proctor has obtained a signed statement in which other villagers vouch for Elizabeth and other accused women. Proctor also learns of Elizabeth's pregnancy from Danforth, which if true, could save her from the gallows for at least a year. Having arrived at a moral crossroads, John must decide what lengths he will go to in order to save his life, as Elizabeth's pregnancy will perhaps save hers. Ultimately he decides that honesty is synonymous with integrity, and he cannot lie or support any further lies.