Thoughts on the meaning of the phrase “the exception that proves the rule:”
I've long thought the phrase “the exception proves the rule” was generally used incorrectly, if not nonsensically. People would use that catch-phrase whenever something disproved a generalization as if the disproof was itself a proof, and I couldn't see any way the phrase could make sense except ironically.
“My dog is friendly,” claims the girl.
The boy reaches down to pet it, and the dog rips his arm off.
“I thought you said your dog was friendly,” says the boy, then passes out from blood loss.
“That's the exception that proves the rule!”
As I said, the phrase didn't seem to make any sense except ironically, but it didn't seem most people were using it ironically. By definition, the phrase seemed self-contradictory nonsense.
Then a while ago a different definition occurred to me. I decided the word “prove” might be meant in the old sense of “to test,” as in a proving ground. An exception that proves a rule would, therefore, be something that tests a rule or calls into question the validity of the rule.
The phrase seemed not to mean that an exception validates a rule, but rather that an exception disputes a rule. Now at least it made sense to me, but if I was right then people seemed to be using the phrase incorrectly. (Much as people say “I could care less” when I suspect they mean “I couldn't care less.”)
For some time I concluded the phrase must mean a testing of a rule, but then one day when I was explaining my take on the phrase (to somebody who, I suspect, couldn't have cared less) I had another thought altogether. This new idea made much more sense, and I've come to believe the phrase must (at least when coined) have been meant this way:
An exception to a given rule proves the existence of that rule.
For instance, if you see a sign that reads “No Parking 4PM-6PM” then you can infer there is a rule that you are permitted to park at other times. If you could never legally park there, the sign would simply read “No Parking.” The fact that the sign is phrased in the form of an exception proves that a contrary rule must exist to which the exception applies.
I like this meaning of the phrase much more. It just feels right. On the other hand, it also means that most people do indeed use the phrase incorrectly. If you say “my dog is friendly” and then your dog bites somebody anyway, you don't have an exception that proves the rule—you just have a nasty dog.
But if you say “my dog doesn't bite people on Saturday or Sunday,” that's an exception that proves the rule your dog should be avoided on weekdays.
Isn't English fun?
