||[Nov. 28th, 2011|03:48 pm]
I know some folks here have discussed "the exception that proves the rule".|
Some have heard (and most people I know of have disliked) the idea of it coming from "every rule has an exception" so an exception proves a rule.
Some have heard an alternate explanation: that an (apparent exception) "proves" the rule, where "prove" refers to "tests", as in a "proving ground" where training/testing is done.
Then I heard a better explanation - and, of course, didn't think to save the article. (But it doesn't matter - it seems to have permeated common internet knowledge, per Google.)
The only meaningful explanation that it had found (keeping in mind that any phrase can become an expression that doesn't actually mean anything) was referring to situations like "curfew on Fridays is relaxed to 10pm". The exception (Friday is *not* the normal curfew) proves that there's a general, earlier curfew "rule". Or, "Parking after noon only permitted on Sunday" "proves" that it's not permitted after noon any other day.
So, essentially, a specific exception proves that, without it, a general rule is in place.
(Now that I've found explanations, Cecil Adams said that it pointed to Cicero, saying that since certain Roman treaties did not allow for citizenship, it "proves" that, if the treaty does not contain that provision, citizenship is allowed. But the much more common use seems to be just an expression without an explicit meaning. http://www.straightdope.com/columns/read/731/whats-the-meaning-of-the-expression-thats-the-exception-that-proves-the-rule, for those who are interested.)