Arthur Kingsmen is a patient because of his impossible, reality-bending mindset. Ripped away from his life, memories broken, he must live the rest of his days fulfilling as an experiment.
Of course, with a power like his, there was always an escape for that. Then again, it's hard enough that he has to remember who he was, and where his best friends were.
('Nother slowburn Lewvithur fic! Updated whenever I struggle with prophetic love.)