Hale enters Salem convinced that there are witches in the town. He is driven to rid the town of these forces. Whether they are the force of the devil or Satan, Hale enters, literally armed with books, ready to rid the town of these forces. It is something that he finds valid with Tituba's confession and those that follow. Hale believes in the authenticity of his convictions and he does not see that there is a difference in his own beliefs and that of authority. This aligns fairly well with what is happening in Salem.
When he starts to communicate with the Proctors and he begins to start seeing how good people like Elizabeth and Rebecca Nurse are being sent up for execution, he starts to recognize that there is something more insidious at work in Salem. This comes out in the trial, as it becomes evident that Abigail and the girls are manipulating the emotional contagion of the time for their own benefit. It also is evident in how Danforth refuses to allow anyone to question any of the evidence established. At this point, especially evident in Act III, Hale recognizes that he has been used by those in the position of Salem's power and vows to separate himself and operate outside of it. In this move, Hale, an apologist for the establishment of Salem, must go outside of it to find truth and justice.