Somewhat related, but when I was sleep deprived and falling asleep during a general relativity lecture in college, I caught myself reasoning through the series of equations written by the professor on the board, and agreeing as to their validity with the explanation in my mind being that my parents are in a foreign country. My brain was convinced it had logically checked the progression and that it made sense, but it was based on this irrelevant fact. The experience always makes me wonder what falsehoods we individually or collectively use to convince ourselves of things being true.