John Proctor is one of the most significant characters in the play, and the one who Miller seems to focus most on as far as the extent to which he changes throughout the play. Miller uses Proctor's character as a way to show many of the themes of The Crucible, including pride and redemption. On a plot level, Proctor is, arguably, the reason that the events escalate in the way that they do. While Abigail should be blamed for sealing the fate of many innocent people, readers can assume that she would not have gone to the extremes that she did had she and Proctor not had their affair.
Proctor's actions throughout the play convey various themes that Miller seemed to want to show with this play. Though Proctor makes a large mistake in cheating on his wife with Abigail, it is very clear that he regrets his actions and want to make things right. At first, when Abigail starts to accuse various people of witcraft, Proctor tries to make things right while still concealing the affair. Eventually, though, he confesses because he believes his confession will make others see Abigail's true character.
A man may think God sleeps, but God sees everything, I know it now. I beg you, sir, I beg you—see her what she is. . . . She thinks to dance with me on my wife’s grave! And well she might, for I thought of her softly. God help me, I lusted, and there is a promise in such sweat. But it is a whore’s vengeance. .
This confession is adimirable and, to some extent, redeems Proctor for what he has done. He truly wants to save his wife and wants to make up for what he has done to her. He believes that he has had a part in what has happened to these women who have been accused, and will confess to an affair if it means saving them.
Toward the end of the play, Proctor is among the accused. Reverend Hale implores him to confess, not because he believes Proctor is guilty, but because he believes his life is more important than the pride of keeping his good name. Eventually, Proctor confesses verbally, but when he is asked to sign his confession for all to see, he refuses, and responds:
Because it is my name! Because I cannot have another in my life! Because I lie and sign myself to lies! Because I am not worth the dust on the feet of them that hang! How may I live without my name? I have given you my soul; leave me my name!
Proctor's refusal to confess on paper is a matter of pride, especially in the eyes of Hale. To him, a life is too precious to waste just because one wants to stand up for the truth. But Proctor refuses to lie and will die with his pride.
To some, though, this refusal to confess is a sort of redemption. He knows he has done wrong, but he is not what they are accusing him of, and he will not allow them to defame him for all to see. For all he has done wrong, he sees this as the one last thing he can do right. This is his redemption, and as much as he has done wrong by Elizabeth, he believes he has done what is right by her by dying for the truth.