An illusion is a false mental image produced by misinterpretation of things that actually exist: 'A mirage is an illusion produced by reflection of light against the sky'.... A delusion is a persistent false belief: A' paranoiac has delusions of persecution'.

Paranoid schizophrenia is when there is a presence of a delusion, a false belief, and possibly a hallucination that fuels that delusion. Types of delusion include delusional jealousy, erotomanic delusion, persecutory delusion, grandiose, and somatic delusion.

delusion

It is certainly a delusion; but the propensity of some religious followers to try and extend that delusion shows that it applies to more than just the self. Also MASS delusion.