We can observe this relatively of illusion (aka agreement) in the various interpretations of the Torah pointed out upthread. I find humorous that video cited by CoinCube, because the two Jewish sects interpretations of the Torah disagree on whether it is kosher to eat a cheeseburger or shawarma:
It may be highly unwise to dismiss proper interpretation of religious dietary restrictions as illusion or meaningless "group think".
See:
https://bitcointalk.org/index.php?topic=1373864.msg17252945#msg17252945