When Reverend Hale first appears in Act I, he is "a tight-skinned, eager-eyed intellectual. [Salem] is a beloved errand for him" (Miller). He believes firmly in what he is doing, and his belief is supported by some of the best scholars and religious figures of the day. The fight against the devil is necessary and all-important, as evidenced by his statements such as "[The books] must be [heavy]; they are weighted with authority" (Miller).
However, Hale strongly believes that his work is a scientific, exact matter that can be weighed and proven empirically. As he explains to Putnam, "Let me instruct you. We cannot look to superstition in this. The Devil is precise; the marks of his presence are as definite as stone, and I must tell you all that I shall not proceed unless you are prepared to believe me if I should find no bruise of hell upon her" (Miller). He carefully seeks evidence in all of his questioning, and he truly believes that what he is doing is right, empirical, and unbiased. Interestingly, many of his questions are biased and leading, and would therefore never be allowed by today's standards, such as when he says to Tituba, "When the Devil comes to you does he ever come - with another person? Perhaps another person in the village? Someone you know" (Miller).
However, by the end of the play, Hale has seen his work turned into a series of wild accusations, and all power has been ripped from his hands. He no longer believes that the work he is doing is good, but likewise he no longer has the power to stop it. It is only once he sees someone else engaging in his "science" that he perceives its flaws. Over the course of Acts Two and Three, he seeks to mollify the bloodthirsty verdicts being passed down by Danforth, such as when he voices his reservation in Act III: "Your Honor, I cannot think you may judge a man on such evidence," to which Danforth chillingly replies, "I judge nothing" (Miller). Later in the same scene, he voices concern regarding the decisions of the court, noting that "it does not follow that everyone accused is part of [the witchcraft]," here using his scientific reasoning to point out a serious flaw: not everyone who comes to court should be found guilty, for this goes beyond the idea of chance and justice (Miller). Hale finally bursts out that he "dare not take a life without there be a proof so immaculate no slightest qualm of conscience may doubt it," clearly distancing himself from Danforth and the court, and ultimately exiting the scene with a cry of "I denounce these proceedings!" (Miller).
By the final act, Hale has been reduced to sarcasm and panic. He presents a simple fact to Danforth: "You must pardon them. They will not budge," and later when asked why he has returned to Salem, he mockingly states, "I come to the Devil's work. I come to counsel Christians they should belie themselves," acquainting the Church and Court's demands that the accused confess to be saved with the sin of falsehood and the devil. Finally, when Proctor crumples his confession, Hale desperately pleads with him to sacrifice his honor and the truth for his life: "Man, you will hang! You cannot!" (Miller).
Hale undergoes one of the most dramatic characterizations, evolving from a well-intentioned, well-educated religious man who believes that his mission is honest and true to a man who finally realizes the corruption and hypocrisy of the proceedings he has begun.