Custom is the whole of equity for the sole reason that it is accepted. That is the mystic basis of its authority. Anyone who tries to bring it back to its first principle destroys it.-- Pensées (Penguin ed. at 46).
... Pascal also has an observation that I could've quoted a dozen times over at the Volokh blog in threads on the constitutionality of the individual mandate:
It would therefore be a good thing for us to obey laws and customs because they are laws . . . But people are not amenable to this doctrine, and thus, believing that truth can be found and resides in laws and customs, they believe them and take their antiquity as proof of their truth (and not just of their authority, without truth).Id. at 216. This is a distinction that lawyers find very difficult to convey to layfolk.
(Quotes taken from Slavoj Žižek's Sublime Object of Ideology, which somehow I did not read in grad school.)