When is a Religious Belief Delusional?

[brewer]

It answers the question for me. What synonym do you suggest that I use? You can be wrong without a belief, delusion includes the belief.

The definition of a belief is an acceptance of something as true or that something exists.  How can you be wrong without holding something as true?

Synonyms are: wrong, mistaken, in error, incorrect.

I was lost and made a wrong turn. I didn't know that so I was mistaken. Not covering my sneeze was incorrect. I made an error in counting. 

None of these need a belief, or at least the same kind of belief as religion/theism. I doubt that you can substitute delusion in the above statements.