Originally Posted by
dan242 I have heard it said that an if-then statement is logically equivalent to a for all-statement.
For example the statement "If x is a natural number then x is a real number" can be rewritten as "For all x such that x is a natural number, x is a real number."
Then consider the statement "If x is a pink alligator then x has seven legs." It is clear that the hypothesis will always be false (because there are no pink alligators) and so the statement is considered trivially true.
Then its logical equivalent statement is: "For all pink alligators x, x has seven legs." And this statement would also be true.
Then consider the statement "If x is a pink alligator then x does not have seven legs." There are no pink alligators so the statement is trivially true, and so it is trivially true that for all pink alligators x, x does not have seven legs.
Then we have the statement, [for all x, P(x)] and [for all x, not P(x)]. I know this is not technically a case of A and NOT A both being true but I was wondering whether there is any other way to resolve this apparent paradox besides saying one statement is not the negation of the other.