When one person suffers from a delusion it is called insanity; when many people >suffer from a delusion it is called religion.
~ Robert M. Pirsig
Now the actual quote's out of the way, here's my version: when one person suffers from a delusion it is called insanity; when many people suffer from a delusion it is called society.
Or friendship, or marriage, or all kinds of other things.
A monthly thread for posting rationality-related quotes you've seen recently (or had stored in your quotesfile for ages).