Aristotle once said “One thing can't be a thing and at the same time it can't be”.

What did he mean? Saying that one thing can't be a thing and at the same time not be a thing? Or, in particular, that a man is a man and enough is enough.

The reason to this statement is that if a man wasn't a man, he wouldn't be a man. And because he's a man, so he's a man.

This may sound very confusing, even like a joke. However, it is possible to find someone who says that a man is not a man, or that this man is not a man.

One example in the bioethics area debates is that there are people who say that a human embryo is not a person, because it lacks a minimum level of development. They define a person in such a way that they exclude embryos.

So, what are human embryos? If they're not people, how do we classify them? Are these animals that will then produce people? The question is not in the way of the discussion, but rather to clarify the ideas. Because if a human embryo isn't a person, then, it has to be something.

That is the other idea that Aristotle had: things have a way of being classified. There is no way that there is a reality that is not something definite. The totally undefined is unthinkable and, therefore, escapes our thoughts and our language.

Aristotle also knew that words make up with everything. It is therefore possible to find an interlocutor willing to deny the obvious, to say things against all logic, to hide behind a curtain of absurd contradictions.

How to act in front of a person like that? It depends. If it is someone of goodwill but with confused ideas, it is possible to start a path of dialogue to clarify terms and thoughts.

On the other hand, if it's someone who's just trying to argue for the sake of arguing, maybe it's best to have a cordial "see you later”.

The doors remain open so that, if attitudes change, we leave aside false contradictions and it is possible to engage in meaningful, reasonable dialogue and able to get a little closer to the truth we desire.