John Proctor is the protagonist in Arthur Miller's play The Crucible for two reasons. Proctor is well respected in the community; his voice stands strongest—and alone in defying and challenging the court, accusing the young girls of being liars. However, his secret relationship with Abigail is central to his Elizabeth's arrest for witchcraft (as Abigail hates her). The second reason Proctor is the protagonist is related to Proctor's choice to take a high moral ground at the end and die rather than lying to save himself—this shows a change of character in Proctor. Proctor is a tragic hero, and a decent man.
While Abigail is behind the spreading madness of a fear of witchcraft, Proctor becomes the central figure within the play. Abigail was dismissed from her position at the Proctor home.
Abigail, is there any other cause than you have told me, for your being discharged from Goody Proctor's service? I have heard it said...that she comes so rarely to the church this year for she will not sit so closed to something spoiled.
Abigail blames her dismissal on Elizabeth Proctor for being a cruel and overly demanding woman—denying Parris' insinuation.
When John Proctor enters in Act One, Abigail openly flirts with him, but he resists her advances, saying:
No, no, Abby. That's done with.
We can assume that John has had an affair with Abigail and that that is the reason she was dismissed. This affair will draw Proctor into the midst of the witchcraft frenzy. Ultimately, Elizabeth stands accused (by Abigail) as do other respectable women in the community. John is outraged.
I'll tell you what's walking Salem—vengeance is walking Salem. We are what we always were in Salem, but now the little crazy children are jangling the keys of the kingdom, and common vengeance writes the law! This warrant's vengeance! I'll not give my wife to vengeance.
In court, the Proctor's servant, Mary, tries to tell the truth about Abigail and the others, but the girls act in such a convincing way that Mary is a witch, that Mary refuses to testify and runs back to Abigail's side, accusing Proctor of being the Devil
Elizabeth cannot be executed because she is pregnant. Proctor must make a decision. If he lies, he can save himself; ironically, if he tells the truth (that he is innocent), he will die. He signs his confession, but refuses to hand it over, especially when seeing the dedication of Rebecca Nurse who refuses to admit to lies, and the others who have died simply for telling the truth—who would not confess to what they had not done. John says:
...I lie and sign myself to lies!...I am not worth the dust on the feet of them what hang.
John is led off to be hanged and Elizabeth refuses to try to stop him, knowing he is doing the morally correct thing—
He have his goodness now. God forbid I take it from him.
John's actions and position within the community, as well as his open defiance of the court proceedings make him the protagonist, driving the plot along. However, he is also a character that goes through a major change in the play, defining what true character and morality are, going to his death because he has come to believe it is so.
[Proctor] is at his most self-aware in his final speech when he realizes the importance of maintaining his integrity.