Is "If A then B" equal to "B if and only if A"?

Lafari@lemmy.world to No Stupid Questions@lemmy.world – 40 points –
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No. They are effectively the same statement.

(A <=> B ) = (A=>B AND B=> A)

Wait. If they are effectively the same statement, wouldn't that mean they ARE equal?

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.

But they switched the order in only the first half of the statement. I don't know if everyone commenting caught that.

Is "If B then A" equal to "B if and only if A"?

This IS different from the original question.

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

Oh yeah. I was very confused as to what that meant, but I learned something today.

Yeah if vs iff can be confusing at first. Trying to understand it with normal grammar doesn't work right. It's a lot more helpful to grok the symbols and so the truth tables by hand to see how they fit together