Why do people believe or disbelieve what they do?

[CG Didymus]

That is a claim, and it hardly warrants certainty.

And how many people have you met and talked to, or had them tell you, how "certain" they were about their religious beliefs? Every believer can say they "certain". But what does that really mean? Like Baha'is when they say they've "proven" it to themselves. Proven what? That their prophet did this, said that and therefore... it must be true?