In John C. Lennox's excellent book God's Undertaker (a philosophical and scientific critique of naturalism, which was recommended to me by Chris Carter), I encountered this quote from Robert Pirsig:
When one person suffers from a delusion, it is called insanity. When many people suffer from a delusion, it is called Religion.
I think I might add: When everybody suffers from the same delusion, it is called "reality."
🙂