It is indeed contingent. The intuitive problem is that "a -> ~b" is not logically equivalent to "~(a -> b)".
The "Counterexample" button shows a world in which the modified statement is false: there is a single man (Socrates) and he is mortal.
Unfortunately, the program doesn't have an "Example" button to show why it is contingent! The empty world is an example, though. This is because the hypothesis (which includes that there is a Socrates) is false, so the statement is vacuously true.
The "Counterexample" button shows a world in which the modified statement is false: there is a single man (Socrates) and he is mortal.
Unfortunately, the program doesn't have an "Example" button to show why it is contingent! The empty world is an example, though. This is because the hypothesis (which includes that there is a Socrates) is false, so the statement is vacuously true.