Give a man a mask and he will show his true face.

The line expresses a paradox Wilde often explored: anonymity can be more revealing than exposure. A “mask” (literal disguise or social cover) reduces the fear of judgment and consequences, loosening the restraints of reputation and etiquette. Under that protection, people may speak more candidly, act more boldly, or disclose desires and prejudices they would otherwise suppress—so the “true face” emerges precisely when the public face is hidden. The idea also critiques social performance: if everyday life requires constant self-editing, then the self that appears when the pressure of being “seen” is removed may be closer to one’s genuine character than the polished persona presented in society.

Commonly circulated variant: "Man is least himself when he talks in his own person. Give him a mask, and he will tell you the truth."