The masked man paradox is a logical argument in which a person is known under one description but not recognized under another. For example, someone knows his father, does not recognize a masked man, and then learns that the masked man is his father. It does not follow that he both knows and does not know his father. Knowing who a person is under one description does not imply recognizing him under every description (Aristotle 1928, §24).
The disguised man, Electra, and the veiled man among the paradoxes of Eubulides have this pattern. The disguised and veiled versions conceal a known person's identity, while the Electra version concerns Electra's failure to recognize her brother Orestes (Hamblin 1970, p. 90). These arguments illustrate why substitution of identical objects inside statements about knowledge need not preserve truth.
