"...Beliefs that would be considered normal for an individual's religious or cultural background are not delusions...

...A delusion is a belief that is clearly false and that indicates an abnormality in the affected person's content of thought. The false belief is not accounted for by the person's cultural or religious background, or by his or her level of intelligence...

...Delusions can be difficult to distinguish from overvalued ideas, which are unreasonable ideas that a person holds, but the affected person has at least some level of doubt as to its truthfulness...."
Source: Encyclopedia of Mental Disorders