Hale believes that witchcraft can be studied, discovered, and expunged much like a disease. When he first comes to Salem from Beverly he arrives a student of witchcraft excited to practice his craft. He is entranced is characterized by his weighty books. These books are heavy in both weight and significance for it is with these books he will "discover" who and who is not affect by witchcraft in Salem.
setting down his books: "They must be; they are weighted with authority."
This is important because Hale truly believes he is helping the people in Salem. He believes that his study has prepared him for this task and that he is ready for it.