"He told you a secret?"
"Why, yes."
"The secret of your great influence over his life?"
"You knew of this secret, then?"
"He didn't tell it to me. Long ago I divined it. Addison is a very interesting fellow to a doctor, and the fact of his strong friendship with you has made him more interesting even than he would otherwise have been. His physique is tremendous. He has a quite unusual vitality, and stronger passions by far than most Englishmen. I confess that my knowledge of human nature led me to foresee a very troubled and too vehement future for him. My anticipation being utterly falsified led me naturally to look round for the reason of its falsification. I very soon found that reason in you."
"I had never suspected it."
"Your lack of suspicion was not the least reason of the influence you exercised."
"Possibly. He told me of the strength of his evil impulses, of how he hated their assaults, and of how being with me enabled him to conquer them. Apparently the contemplation of my unnatural nature is an armour to him."
"It is."
"Well, I continued to bewail my condition, which he envied, and it ended in our sitting down, in jest, to make an experiment to try to exchange our souls."