"At the beginning he somehow convinced himself that his soul didn't really exist, despite the presence of a literal devil in front of him, offering the power to do genuine magic."
To be fair, if a "devil" suddenly showed up in front of me, offering me anything I ever wanted in exchange for my "soul", my worldview would not change. Since this "devil" exists, it is part of the natural world, I just can't know exactly what it is or where did it came from. I might as well accept the offer this alien/ultra advanced AI/simulation being/whatever offers me, since this simple fact of something appearing out of nothing is not in any way a proof of God's existence, or of souls being a thing etc. If that was the case, when the Europeans arrived in America, with gunpowder and ocean capable ships, the natives should have, obviously, accepted as fact that they were gods... well, it didn't end well for the Aztecs.
To be fair, if a "devil" suddenly showed up in front of me, offering me anything I ever wanted in exchange for my "soul", my worldview would not change. Since this "devil" exists, it is part of the natural world, I just can't know exactly what it is or where did it came from. I might as well accept the offer this alien/ultra advanced AI/simulation being/whatever offers me, since this simple fact of something appearing out of nothing is not in any way a proof of God's existence, or of souls being a thing etc. If that was the case, when the Europeans arrived in America, with gunpowder and ocean capable ships, the natives should have, obviously, accepted as fact that they were gods... well, it didn't end well for the Aztecs.