Miller tells us that initially, Hale "conceives of himself much as a young doctor on his first call...he feels himself allied with the best minds of Europe - kings, philosophers, scientists, and ecclesiasts of all churches." He shows up on the scene with loads of books believing that "the Devil is precise" and can be calculated, detected, and crushed. He believes he has successfully found witches in other places, and is now an expert.
As more and more people are accused, he states he trusts in God and the justice of the court to free those who are not guilty. But when he hears Giles and Proctor defending their wives, Hale himself begins to question the court. Unlike the judges, Hale sees the sense in the evidence being presented. Proctor's condemnation at the end of Act Three finally causes him to snap and realize the insanity of the proceedings.
Hale is humbled by this realization and spends Act Four trying to make up for his wrongs by getting prisoners to confess. He admits to Elizabeth that he had come into the village with confidence and from that time everything he had touched died. He feels responsible for the lives that have been condemned.
When Reverend Hale arrives in Salem, he is an egotistical man, much like many of the religious men during that time. He had been credited with finding witches in the past and has quite a reputation. He's very quick to believe there are witches in Salem because the Puritans believed that evil was all around them. Hale begins to questions this, however, as the play continues because respectable people like Rebecca Nurse are arrested. It's then he becomes suspicious of the motives of the girls and some other people in Salem, such as Putnam. He goes to warn John and Elizabeth Proctor about doing what is right to prove they are good people who trust in God, such as attending church and having their child baptized. Once the Proctors are arrested, Hale realizes that the girls have been lying all along and refuses to have anything more to do with the court. He spends the last act trying to convince Rebecca Nurse and Proctor to confess, so they can save their lives. He feels guilt that he was ever a part of the witch hunt and tries to redeem himself in the end.
Reverand Hale had a firm belilef in his books, and the somewhat lucky experiences he has had in dealing with witchcraft. Upon his arrival, he is almost smug with confidence in his ability to manage this situation. Yet, as the hysteria grows, and the town becomes bloodthirsty, Hale realizes that he is in no way prepared to deal with this situation. He also realizes that it is not "Witchcraft" at play, as well.