▲ 40 ▼ Is "If A then B" equal to "B if and only if A"? (lemmy.world) submitted 2 years ago by Lafari@lemmy.world to c/nostupidquestions@lemmy.world 60 comments fedilink hide all child comments
[–] Apepollo11@lemmy.world 17 points 2 years ago (1 child) You've have some examples, but in case they are not clear enough: If [you have AIDS] then [you are unwell] [You are unwell] if and only if [you have AIDS] The first one is not the same as the second. Why? There are plenty of ways to be unwell, without necessary developing AIDS. The first statement only defines one possible path to B, not all of them. permalink fedilink source hideshow 2 child comments replies: [–] AmidFuror@kbin.social 7 points 2 years ago (1 child) Not just HIV, but full blown AIDS? permalink fedilink source parent hideshow 2 child comments replies: [–] BananaTrifleViolin@kbin.social 7 points 2 years ago* (1 child) Actually a good example: If you have AIDs (A) then you have HIV (B). True You have HIV (B) if, and only if, you have AIDS (A). Not true If you don't have HIV (B), then you don't have AIDs (A). True, and the actual inverse of "If A then B"; which is "If not B, then not A" permalink fedilink source parent hideshow 2 child comments replies: [–] AmidFuror@kbin.social 5 points 2 years ago It's important to stress the "full blown" modifier in any example. permalink fedilink source parent
[–] AmidFuror@kbin.social 7 points 2 years ago (1 child) Not just HIV, but full blown AIDS? permalink fedilink source parent hideshow 2 child comments replies: [–] BananaTrifleViolin@kbin.social 7 points 2 years ago* (1 child) Actually a good example: If you have AIDs (A) then you have HIV (B). True You have HIV (B) if, and only if, you have AIDS (A). Not true If you don't have HIV (B), then you don't have AIDs (A). True, and the actual inverse of "If A then B"; which is "If not B, then not A" permalink fedilink source parent hideshow 2 child comments replies: [–] AmidFuror@kbin.social 5 points 2 years ago It's important to stress the "full blown" modifier in any example. permalink fedilink source parent
[–] BananaTrifleViolin@kbin.social 7 points 2 years ago* (1 child) Actually a good example: If you have AIDs (A) then you have HIV (B). True You have HIV (B) if, and only if, you have AIDS (A). Not true If you don't have HIV (B), then you don't have AIDs (A). True, and the actual inverse of "If A then B"; which is "If not B, then not A" permalink fedilink source parent hideshow 2 child comments replies: [–] AmidFuror@kbin.social 5 points 2 years ago It's important to stress the "full blown" modifier in any example. permalink fedilink source parent
[–] AmidFuror@kbin.social 5 points 2 years ago It's important to stress the "full blown" modifier in any example. permalink fedilink source parent