"The exception that proves the rule" - Please explain what this phrase means to you

“The exception that proves the rule”

I’ve sometimes heard this phrase used when someone is rebutting an example that does not correspond with their argument, but I’ve never really quite grasped how an exception can “prove” or “test” a rule. It’s an exception. It contradicts the rule. Obviously I’m mis-understanding some aspect of the meaning.

Please assist.

Tom Burnam, The Dictionary of Misinformation:

i have always heard it as joke meant to try to regain a little face through humour after some counter example made your argument look like the apple that fell into a vat of live starving apple worms.

cecil did an article about it here

The standard explanation is that it refers to the archaic use of ‘prove’, which meant ‘test’. Cannon were proved by having hefty mean belt the crap out of them with hammers for example. If they didn’t crack they were safe to fire. The term ‘proving ground’ was still relatively common early this century. The expression “prove yourself as a man” still hangs on to the archaic use, although I have noticed in the past few years people are writing “prove to yourself that you are a man” or “improve yourself as a man” so that too is losing its meaning, So an exception proved a rule in the truest Socratic tradition of testing the rule against possible contradictory situations. As the definition of ‘prove’ gradually shifted people began to misapply the expression, until today it no longer means what it is intended to.

This sounds plausible enough, and that is certainly a use of prove seen commonly in even moderately old writings. However I don’t know how old the actual expression is.

OK … I suppose that makes sense. So… it’s an exception that’s testing the validity of the rule by existing. If that’s the case, why do people throw out this phrase to the person pointing out a situation in which their argument manifestly does not apply, as if they have sucessfully rebutted the counter-point.

Person A - Women are too emotional to think clearly about legal issues.

Person B - You mean to tell me you think Sandra Day O’Conner of the SCOTUS is too emotional in her judgements?

Person A- Just so! She’s the exception that proves the rule!
What the hell has person A really said, other than a somewhat hollow, “She’s an exception to the norm” assertion?

When I was learning to drive, I could never remember if U-turns were legal in Alabama, in general. How did I finally convince myself that they were? Because of the existence of “No U-turn” signs.

For what it’s worth, what the saying means to me is that the exceptions contained within a rule give insight into the limits of the rule.

For example, let’s suppose the constitution says " . . . the right of the people to keep and bear arms shall not be infringed, except that Congress may regulate the concealed carry of arms."

Based on the the exception, it would appear that one has a constitutional right to openly walk around with a pistol on one’s hip.

I have no idea if this is what the phrase originally meant or actually means though.

You got it spot on Astro. All that person A has said is “She’s an exception to the norm”.

The expression is mostly misapplied these days. That’s common enough with cliches that ahve changed their meaning over the years. It’s frighteningly common to hear people say that Suffer the little children" means that children should suffer.

People are misusing the expression. That’s all. It has gone from a reasonable statement to a lame cliche for people whose arguments don’t make sense. Don’t expect sense out of cliches.

I think this is a lot easier to understand when you remember the usage “As a rule…” which means generally or usually. If the only exceptions you can identify are clearly unusual or unlikely, that proves the rule.

For what it’s worth, I did a google search and found the following:


sorry if I quoted too much!!

Interesting lucwarm. Looks like Achernar was right.

So… “The exception proves the rule” means that directly or obliquely referencing that a special leave or exception exists in a situation *** implies*** that rule exists. Fine, I understand now.

Therefore, in this contextual understanding of the phrase, for someone in an argument to reply to a counter-example with this general purpose rhetorical cliche, “that’s the exception that proves the rule”, is non-sensical, unless it is an agreed on fact in the discussion that the counter example is “special”, when in fact the counter arguer is often making precisely the opposite point.

Actually, cannon and rifle barrels are “proved” by firing them with a much larger than recommended powder charge. If they don’t explode when greatly overloaded, they’re safe to fire with a normal charge.

The phrase “the exception that proves the rule” means nothing. I’d just ignore it.


You’re right as to the technical meaning. And since most folks misuse the phrase, it’s become all but useless for its intended purpose.

That doesn’t mean they won’t use it and think they’ve said something, but it does mean you and I are free to badger them back to explain what they’re really trying to say.

Fighting ignorance is taking lots longer than Cecil said it would.

I have heard people claim that since “there’s an exception to every rule”, a rule is not a rule unless there’s an exception to it.

Could it be that peoples’ misunderstanding of the archaic definition of ‘prove’ started the phrase, but the justification above has helped perpetuate the phrase’s use?

Just for clarification: If I saw something saying “Only on Tuesdays are you allowed to wear hats in the gymnasium,” I could (using the cliche) figure out that you’re not allowed to wear hats on other days?

I have heard people claim that since “there’s an exception to every rule”, a rule is not a rule unless there’s an exception to it.{/quote]

To which annoying 3rd graders reply: “But that rule can’t be true unless it has an exception, and if it has an exception, it’s not true”

At which point, the adult usually explodes. Well, not literally (though it would surely be natural selection in action) but in the rather more unpleasant fashion allowed by Article I Section VIII subsection © of the Monkey Logic Code, i.e “Any sufficiently larger monkey may punish, torture or abuse any sudfficiently smaller monkey to conceal their own shortcomings or humiliation”

Actually what I said is perfectly correct. Cannon were proved by having hefty men belt the crap out of them with hammers. I have the references available if you really want to dispute it.

So the “proving ground” would be the big, open firing range where they. . . hammered on the cannon barrels?

Stand clear, everyone.

No, you can figure out that the rule exists without the cliche in that case. If the sign said “Hats allowed on Tuesday” then the cliche indicates that there must be a rule that generally there are no hats allowed. At least, that is how I read it.