The answer to this one can be found in the beginning of Act four. At the beginning of this act, several highly reputable people are set to hang: Rebecca Nurse, Martha Corey, and John Proctor. These are people that the townsfolk respect and look up to, who were well-liked and had influence in the town. Parris is worried that if they hang, the townspeople will rebel and overthrow the courts. He has already seen the town turning against him; he found a knife stuck in his door that morning, and Abby had just skipped town. Things aren't looking good for him. He is worried that the townspeople will finally be fed up with the hangings and stage a rebellion, which might be dangerous to him. So, Parris thinks that if Proctor will confess, maybe that will set an example for the others, and they will all confess. If they do confess, they won't hang, and maybe the townspeople won't get so angry, and he will be safe.
Hale wants Proctor to confess for different reasons; he doesn't care if the townsfolk rebel. In fact, he wishes it would happen. Hale has been striving with all of the accused, trying to convince them to confess in order to save their lives. As he puts it to Elizabeth Proctor, God damns a liar less than one who will die for pride. Hale simply wants people to stop getting hanged. He feels responsible for their deaths, and is trying to keep people from hanging because they won't confess. He feels that if Proctor confesses, his life will be saved, and maybe that will convince the others to confess and save their lives too.
I hope that those thoughts help; good luck!