'Genealogy' is an expression that has come into currency since the 1970s, a result of Michel Foucault's works Surveiller et punir (1975) (Discipline and Punish, 1977) and the History of Sexuality (1976, 1984a, 1984b). Foucault's use of the term continues Nietzsche's in his On the Genealogy of Morals ([1887] 1967). For both philosophers, genealogy is a form of historical critique, designed to overturn our norms by revealing their origins. Whereas Nietzsche's method relies on psychological explanations, and attacks modern conceptions of equality in favour of a perfectionist ethic, Foucault's relies on micro-sociological explanations, and attacks modern forms of domination in favour of radical politics.