This comes from a guy considered by many to be the most skilled of the ancient Greek orators, the statesman Demosthenes of Athens, and the following quote attributed to him is enormously relevant to modern skeptics, namely, the topic of self-deception.
Even though some pseudoscientists do turn out to be charlatans, it’s often extremely difficult to definitively identify someone as either an intentional fraud or just self-deluded believers without knowing them and their personal history inside and out.
There’s the risk of committing a False Dilemma fallacy on insufficient information.
It’s often not just one or the other, though, and frequently it turns out to be an odd mix of the two when the crank’s true motives can be identified at all…the well-known phenomenon of the pious fraud who truly believes their own claims, but isn’t above a little dishonesty and corner-cutting to promote them.
The reasons and psychological mechanisms for self-delusion are many…
Again, not an easy task for a n00b like me, which is why it’s a good idea for me at this point not to jump to conclusions until the evidence is in…and even then, there’s no way to be certain short of actually getting inside his head, and I ain’t psychic.
Anyhoo, here’s the quote:
A man is his own easiest dupe, for what he wishes to be true he generally believes to be true.
— Demosthenes (Δημοσθένης) (384 BC – 322 BC)