How does John Proctor represent integrity in The Crucible?

This play presents a
number of conflicts, external and internal. The crisis faced by John Proctor in the final two
acts of the play embody both of the external and the internal conflicts of the story as he is
forced to confess to a moral transgression then accused of another. 

Each of
these conflicts, for Proctor, is directly related to integrity. 

When Proctor
confesses to his affair with Abigail while in court, he does so because his sense of integrity
demands it. His wife has been sentenced to die. Proctor has a choice to make - either maintain
his secrecy regarding his affair with Abigail or confess, sacrifice his reputation, and in this
way try to save Elizabeth. 

This is an issue of integrity. Proctor realizes
that if he maintains his secrecy, he will be acting in cowardice, betraying his wife (after
already wronging her with Abigail), and failing to do the self-less thing. As a man who values
honesty, Proctor cannot lie by omission. He cannot keep his secret. He must confess. 

His confession to the affair leaves his integrity intact, even while it damages his
repuation as a moral man. 

Later, Proctor faces a final test. He will be
hanged if he continues to deny that he has performed witchcraft. Though he is tempted to lie to
save his life and provide a false confession, Proctor realizes again that this is an issue of
integrity. 

In Proctor's final recantation of his
confession and his refusal to put his principles aside to save his life, we see the triumph of
personal integrity in a world of moral uncertainty.

Choosing honesty, a supreme value for Proctor, is his method of maintainting his
integrity.