• Boinkage@lemmy.world
            link
            fedilink
            arrow-up
            7
            arrow-down
            1
            ·
            edit-2
            6 months ago

            Substitute common sense terms. If I say “if it is an apple, it is a fruit”, does it then follow that a thing is a fruit if and only if it is an apple? No. Lots of other things are fruit without being an apple.

            • Rhynoplaz@lemmy.world
              link
              fedilink
              arrow-up
              1
              ·
              6 months ago

              Better read that one again.

              “If B then A” … “B if and only if A”?

              If Apple then fruit. Is Apple ONLY if it’s a fruit.

              This one actually checks out.

          • Casey_Masterpiece@lemmy.world
            link
            fedilink
            arrow-up
            2
            ·
            6 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.