This is an example of how an argument could contain perfect logic and still be wrong. There are two ways that an argument can be wrong. There can be an error in the reasoning of the argument, which will be the far more common type of flawed argument we see, and there can be a premise that is not true. This is an example of the latter.
The statement that anyone named sue is a girl, and thus if we see sue we know she is a girl is logically valid. We define a category, and then apply that definition to an individual.
However the definition can simply be wrong. The logic may be fine if we assume the premise is correct, but the premise itself is not true. There could absolutely be a boy named sue. This illustrates the kinds of ways we will see flawed arguments, although to reiterate the overwhelming majority of flawed arguments we see will be flawed because their reasoning is flawed, not because of a bad premise.
