Comment by lelanthran | Hacker News Reader

Comment by lelanthran | Hacker News Reader

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> That's not what an exception proving a rule means. It has a technical meaning: a sign that says "free parking on sundays" implies parking is not free as a rule.

So the rule is "Free parking on Sundays", and the exception that proves it is "Free parking on Sundays"? That's a post-hoc (circular) argument that does not convince me at all.

I read a different explanation of this phrase on HN recently: the "prove" in "exception proves the rule" has the same meaning as the "prove" (or "proof") in "50% proof alcohol".

AIUI, in this context "proof" means "tests". The exception that tests the rule simply shows where the limits of the rules actually are.

Well, that's how I understood it, anyway. Made sense to me at the time I read the explanation, but I'm open to being convinced otherwise with sufficiently persuasive logic :-)

The rule is non-free parking. The exception is Sundays.

The meaning of a word or expression is not a matter of persuasive logic. It just means what people think it means. (Otherwise using it would not work to communicate.) That is why a dictionary is not a collection of theorems. Can you provide a persuasive logic for the meaning of the word "yes"?

https://en.wikipedia.org/wiki/Exception_that_proves_the_rule

Seems like both interpretations are used widely.

The origin of the phrase is the aphorism that "all rules have an exception". So, when someone claims something is a rule and you find an exception, that's just the exception that proves it's a real rule. It's a joke, essentially, based on the common-sense meaning of the word "rule" (which is much less strict than the mathematical word "rule").

50% proof alcohol? That isn’t how that works. It’s 50% ABV aka 100 proof.

> 50% proof alcohol? That isn’t how that works. It’s 50% ABV aka 100 proof.

50% proof wouldn't be 25% ABV?

Since 50% = 0.5, and proof doesn't take a percentage, I believe "50% proof" would be 0.25% ABV.

Good catch :-)

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