“The exception proves the rule.”
Most people seem to think that this means that an exception to a rule proves that the rule exists. They often use this as an excuse to break the rule.
“Prove” is an old word for “test.” What the expression really means is that if you test the rule by breaking it, and get into trouble for it, the rule is real. Not quite the same thing.
Side note: The only time in the Bible where God invites people to test Him is in Malachi, which reads, in the King James, “Prove me now herewith…” I leave it as an exercise for the reader to find what the test is.
How’s your older English? Got any useful archaisms to share? Make a comment.