What a man believes upon grossly insufficient evidence is an index into his desires – desires of which he himself is often unconscious.
If a man is offered a fact which goes against his instincts, he will scrutinize it closely, and unless the evidence is overwhelming, he will refuse to believe it.
If, on the other hand, he is offered something which affords a reason for acting in accordance to his instincts, he wil accept it even on the slightest evidence.
The origin of myths is explained this way.
– Bertrand Russell