witchcraft, even more so than another minister, and he explains that he will not take kindly to being doubted in his decisions.  In fact, he refuses to move forward in his investigation unless he can be guaranteed that his judgment will not be questioned.  

Further, in regard to those weighty books, Hale says,

Here is all the invisible world, caught, defined, and calculated.  In these books the Devil stands stripped of all his brute disguises. . . .   Have no fear now—we shall find him out if he has come among us, and I mean to crush him utterly if has shown his face!

Hale is unconcerned that the Devil might outsmart him and is entirely confident that he and his arsenal of knowledge will not only best the Devil, but also destroy him.  This is pride, indeed: interesting for a minister certainly.

At the end of act three, Hale has become convinced of the corruption in the Salem court. He leaves, shouting, "I denounce these proceedings, and I quit this court!" He then leaves the accused people of Salem to fend for themselves.  However, in the beginning of act four, Hale returns, singing a very different tune.  To Elizabeth Proctor, he now says,

Let you not mistake your duty as I mistook my own.  I came into this village like a bridegroom to his beloved, bearing gifts of high religion; the very crowns of holy law I brought, and what I touched with my bright confidence, it died; and where I turned the eye of my great faith, blood flowed up.

Hale now understands the pride with which he entered the town, and he knows that he is partially responsible for the course the accusations and trials have taken.  In fact, he tells Danforth, "There is blood on my head!  Can you not see the blood on my head!!"  He has returned to try to convince the convicted to lie and confess to witchcraft in order to save their own lives because he now believes that lying is better than giving up one's life for no other reason than one's pride.  He is clearly conflicted by his role, calling it "the Devil's work," but he is also trying to soothe his conscience and do right by these innocents, whom he left before at the court's mercy.

One of the ways you can tell Reverend Hale is enthusiastic is because there are often exclamation points at the ends of his lines. Since this is a play, a lot of the characterization comes through dialogue. A lot of exclamation points show Hale is either shouting or excited. 

HALE: Putnam! I had not expected such distinguished company, sir.

PUTNAM: It does not seem to help us today, Mister Hale. We look to you to come to our house and save our child.

HALE: Your child ails, too (Act I)?!

Reverend Hale is the supposed expert on witchcraft. When he first comes in, he has heavy religious books, which he announces are weighted with authority. He never questions whether he is right, and basically finds witchcraft because he is looking for it.

Hale really believes in witchcraft. He thinks the devil is at work in the young women of Salem. Anyone could be at fault. A true believer, Hale is even more dangerous than the lying schemer Abigail.

HALE: Have no fear now — we shall find this devil out if he has come among us, and I mean to crush him utterly if he has shown his face! (Corey crosses near bed, looking at Betty.)

REBECCA: Will it hurt the child, sir?

HALE: I cannot tell. If she is truly in the Devil’s grip we may have to rip and tear to get her free (Act I).

With Hale's presence adding legitimacy to the proceedings in the Salem trials, things get out of control quickly. Hale pushes forward even though it should have been obvious it was just a bunch of girls who got in trouble and made up lies to cover themselves. Since witchcraft was what Reverend Hale was called to find, he finds it.