Hypocrisy is the practice of feigning what one is not or professing what one does not believe.^[1] The word "hypocrisy" entered the English language c. 1200 with the meaning "the sin of pretending to virtue or goodness".^[2] Today, "hypocrisy" often refers to advocating behaviors that one does not practice. However, the term can also refer to other forms of pretense, such as engaging in pious or moral behaviors out of a desire for praise rather than out of genuinely pious or moral motivations.

Definitions of hypocrisy vary. In moral psychology, it is the failure to follow one's own expressed moral rules and principles.^[3] According to British political philosopher David Runciman, "other kinds of hypocritical deception include claims to knowledge that one lacks, claims to a consistency that one cannot sustain, claims to a loyalty that one does not possess, claims to an identity that one does not hold".^[4] American political journalist Michael Gerson says that political hypocrisy is "the conscious use of a mask to fool the public and gain political benefit".^[5]

Hypocrisy has been a subject of folk wisdom and wisdom literature from the beginnings of human history. Increasingly, since the 1980s, it has also become central to studies in behavioral economics, cognitive science, cultural psychology, decision making, ethics, evolutionary psychology, moral psychology, political sociology, positive psychology, social psychology, and sociological social psychology.