“Masked man” (fallacy)
You see a man wearing a mask.
Because of the mask, you do not recognise that it is your father.
That is, you do not know who the masked man is;
But at the same time you know who your father is.
Therefore, you know the masked man and at the same time you do not know him.
In this story, the terms “masked man” and “your father” refer to the same person (extension), but yet at the same time the same person is referred to in different ways (i.e. the intention differs). The resulting contradiction leads to a paradox here.
For more information, please see: Intensional fallacy.