Proctor is a sharply intelligent man who can easily detect foolishness in others and expose it, but he questions his own moral sense, because of his affair with Abigail Williams.
In the quote above, Proctor questions whether or not he is a moral man, yet this past event is the only major flaw attributed to Proctor, who is in all other respects honorable and ethical.
It is a sign of his morality that he does not feel himself adequate to place himself as a martyr for the cause of justice when he is given the choice to save himself at the end of the play.
Proctor’s character contains a caustic blend of pride and self-loathing, a very puritanical combination indeed! His self-esteem sets him apart from other members of the town, such as the Putnams, who feel one must obey authority at all costs. Instead, John Proctor speaks his mind when he sees injustice. Throughout the play, he openly disagrees with the actions of Reverend Parris, an action that ultimately leads to his execution.
Despite his prideful ways, John Proctor describes himself as a "sinner."