Answer:
Questioned him to gain privileged information.
Step-by-step explanation:
Towards the end of the passage, we learn from the speaker that Bradford was a crafty old sophister.
Sophisters or sophists were pre-Socratic philosophers whose domain of expertise were skills that can be compared to modern day advocacy, manipulating arguments so as to convince their interlocutors of anything at anytime.
The primary meaning of the word art is skill, artful here meaning skillful. If Bradford were a sophister, that would mean he knew just what to say or do, in order to get what he wanted. And it is exactly what he did. He managed to go unnoticed and get the information he wanted from Keimer thanks to his artful questions.