The exception that proves the rule.
What's different about computers that makes this applicable here?
It's one of those terms where I am pretty confident that I see the original use more rarely than the technically incorrect variations to the point I'd hesitate to call them incorrect any more.
So no, OP used the correct definition and no wide spread usage uses ~Q=>~P. That's a weird logical formulation that was randomly concocted.
https://en.wikipedia.org/wiki/Exception_that_proves_the_rule
Said another way:
Rule: It's hard to find a product that hasn't gotten worse or more expensive, even adjusted for inflation.
Exception: computers i think are more affordable now than even 20 years ago, in bang for buck
This proves the rule because if it's an exception to the rule, therefore the rule must exist in the first place.
Poster 1: everything is worse
Poster 2: but compute has gotten better
Poster 3: that’s the exception to the rule that everything has gotten worse, proving the rule exists
Poster 2 has raised a disagreement with the original claim. There was no implied rule. Poster 3 used the claim of it being an exception to imply a third rule that neither of the first two posters had claimed, as opposed to making a statement where the exception demonstrated the existence of a rule in the first place.
If you're going to make false claims and lie about my intent, then at least don't be entirely wrong while doing it.
If you're going to continue this thread you can talk to yourself - I have no interest in continuing a discussion when you start lying about my intent.
No, most logically coherent usage of that phrase absolutely does reflect ~Q=>~P, which was not "randomly concocted", but was rather was determined via logical reasoning.
> Rule: It's hard to find a product that hasn't gotten worse or more expensive, even adjusted for inflation.
> Exception: computers i think are more affordable now than even 20 years ago, in bang for buck
> This proves the rule because if it's an exception to the rule, therefore the rule must exist in the first place.
No, a standalone claim that contradicts the premise of a previously claimed general rule does not "prove" that original claim.
If I say "it hasn't rained all week" and you respond with "but it did rain on Tuesday", you're pointing out evidence that falsifies the general claim about it not raining, not demonstrating an exception that strengthens its validity otherwise.
This usage only makes sense if the "exceptional" claim is formulated as an exception to some unstated assumption, but even there, does not actually substantiate the validity of that assumption, but rather just reveals that the assumption is being made.
Another commenter offered a good example of this: "no parking on Saturdays" carries the implied premise that parking is permitted on other days of the week: it's nature as an imperative statement that applies special treatment to a particular case implies that the general case is something else.
But "computers have become cheaper over the past 20 years" does not in itself imply any assumptions about general economic trends or other categories of goods, and certainly doesn't prove the validity any assumptions about either.
If a sign says “No parking on saturdays”, that is an exception that can be used to infer the rule “parking here is okay the rest of the time”.