That is not correct.
When the antecedent (the first, "If" part) of a conditional is true, then the consequent (the second, "then" part) must be as well. So, if the consequent is FALSE, the antecedent can't be true. In other words, imagine that all vampires are undead. Something that is NOT undead can't be a vampire; because if it WERE a vampire, it would have to be undead.
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