It's possible that I came to my conclusions purely through philosophical reasoning, and that I am suffering the sort of defect that famously consumed Cantor or Gödel or Pirsig. It's easy to say, "I'm not crazy! You're the one who's crazy!" Or perhaps there is a repressed childhood of abuse somewhere in the memories, but who can tell whether repressed memories are a real thing, or whether memories are trustworthy in general.
At the same time, though, people delude themselves all the time. It's a cultural thing; I think that memetics is the right field of study for figuring out how that works. And once one starts to realize how delusional their cultural beliefs are, one cannot help but start examining themselves. Upon learning about p-zombies, for example, I realized that I must be a p-zombie, because I had no evidence to the alternative and no way to refute the argument.