At first, the audience might find him to be just as self-righteous as Rev. Parris. However, Hale seeks out witches because in his own misguided way he wants to rid the world of evil. He speaks as though his methods are logical and scientific, when in fact he uses wives' tales and mythology to root out so-called demons.
One of the more interesting lines from the play is when Reverend Hale is speaking with Parris and the Putnams. They claim that witches are in Salem, but he contends that they should not jump to conclusions. He states, "We cannot look to superstition
in this. The Devil is precise." Arthur Miller notes that this line "never raised a laugh in any audience that has seen this play." And why should Hale's line generate laughter? Because, at least in Miller's reckoning, the concept of the Devil is inherently superstitious. Yet, to people such as Hale and many audience members, Satan is a very real person and therefore the Devil's work should be indentifiable.
His change of heart, however, stems from his intuition. Ultimately, in the climactic third act, Hale feels that John Proctor is telling the truth. The once-idealistic reverend openly denounces the court, but it is too late. The judges have already made their deadly ruling. Rev. Hale is heavy with guilt when the hangings take place, despite his prayers and fervent protests.
http://plays.about.com/od/plays/a/rhale.htm
By Wade Bradford, About.com Guide