Comment on Is "If A then B" equal to "B if and only if A"?
Lafari@lemmy.world 9 months agoIs “If B then A” equal to “B if and only if A”?
Comment on Is "If A then B" equal to "B if and only if A"?
Lafari@lemmy.world 9 months agoIs “If B then A” equal to “B if and only if A”?
Thoth19@lemmy.world 9 months ago
No. They are effectively the same statement.
(A <=> B ) = (A=>B AND B=> A)
Rhynoplaz@lemmy.world 9 months ago
Wait. If they are effectively the same statement, wouldn’t that mean they ARE equal?
Casey_Masterpiece@lemmy.world 9 months ago
If B then A is the same as if X then Y is the same as if A then B. They are saying it’s the same as the OP. Changing the letters around doesn’t change the meaning since the letters are just placeholders.
Now if you said If A then B AND If B then A as one it wouldn’t be the same because A and B would have to keep the same meaning.
Rhynoplaz@lemmy.world 9 months ago
But they switched the order in only the second half of the statement. I don’t know if everyone commenting caught that.
Thoth19@lemmy.world 9 months ago
I mean it is the definition of “if and only if”. And by commutativity we also know that A iff B is equal to B iff A
zenharbinger@lemmy.world 9 months ago
Also, Not (A XOR B)