Eubulides of Miletus (c. 400 BC), a philosopher of the Megarian school and a student of Euclid of Megara (not to be confused with Euclid of Alexandria who compiled the Elements of Euclid), posed the following paradox:
You say you know your brother.
Yet when your brother is hooded you are unable to identify him.
Therefore you both do and do not know your brother.
This is called the Hooded Man paradox. It is one of the four major paradoxes attributed to Eubulides, the other three being “The Heap”, “The Liar” and “The Horned Man”.
Personally, I don’t have a brother so I can’t surely tell whether I would be able to recognize him if he’s wearing a hood. However, if, hypothetically, I have a brother, I’m pretty confident that I woild be able to discern his identity based on things like his physique, mannerisms and actions even if he’s wearing a hood. But who knows… Now, that just sounded like a paradox too.