News for hackers. Stuff that matters.

A comment on Asian-American Students Suing Harvard Over Admissions Win Justice Dept. Support. Parent comment

Re:Asian-American Students Suing Harvard Over Admissions Win... by dunpeal on Thursday August 30, 2018 @12:55PM (#17878288)
> "We would not need affirmative action if [reality was different]." > Ergo, we need affirmative action.

Logical fallacy.

"I have a good immune system, so I would not need medicine if I got a cold."

Doesn't mean I need medicine right now, when I'm not sick at all.

EDIT: The example seems to be confusing people, so here's a more formal explanation:

if (reality is different) then not (we need affirmative action)

Does not imply:

if not (reality is different) then (we need affirmative action)

The original claim is P-> ~Q

It doesn't follow that ~P -> Q

[ Parent | on HN ]
Re:Asian-American Students Suing Harvard Over Admissions Win... by adarsh_p on Thursday August 30, 2018 @01:06PM (#17878416)
The inverse of your example sentence would be something like - "I don't have a good immune system, so I would need medicine if I got a cold" - which makes sense, and is analogous to "Reality is not different, so we do need affirmative action."
[ Parent | on HN ]
Re:Asian-American Students Suing Harvard Over Admissions Win... by nostrademons on Thursday August 30, 2018 @01:13PM (#17878522)
The inverse of a proposition is not logically entailed by the proposition itself. You're looking for the contrapositive, but the contrapositive of his example is "I need medicine if I got a cold, so I do not have a good immune system."
[ Parent | on HN ]
Re:Asian-American Students Suing Harvard Over Admissions Win... by adarsh_p on Thursday August 30, 2018 @09:29PM (#17882264)
Got it, thanks for the explanations!
[ Parent | on HN ]