Yeah, I've heard that apple-expression with both barrel and bunch!
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The only expression I've ever heard containing both "exception" and "rule" is the one you mention, Laura: "The exception proves the rule."
The reason why this expression seems illogical
(and therefore why you doubted your own memory, perhaps) is that it contains the archaic use of the verb "to prove," which really means "to
test" in modern English, i.e.:
The way to see if your "rule" is true or not is to
test it, with seeming "exceptions" to it.
Then you'll come up with a more accurate and comprehensive form of the rule, which will apply to a greater range of cases, previous "exceptions" included.
The way we use "the exception proves the rule" today seems to almost be a joke, dismissing the occasional incidence of something as random chance, I think:
"John didn't drink too much last night."
"Oh well, the exception proves the rule!"
But the original meaning seems to be rather that "you can use exceptions to test the rules you believe in."
Hmmm...This expression has always been one that intrigued me as well... 