This chapter proposes to analyze the nature of moral responsibility. It does not explore how moral responsibility is practiced in specific cultural communities, in certain periods of time, or what kind of cognitive biases are observed according to social circumstances (Heider 1958; Weiner 1995). My concern is neither how human beings learn the attribution pattern of responsibility (Piaget 1932; Kohlberg 1981), nor what is the best conceptualization of moral responsibility. The first approach, typically socio-psychological, addresses biases of accounting for a criminal deed, but does not ask what moral responsibility is; the second, developmental, studies children's evolution in causal attribution of responsibility, but does not determine what moral responsibility is; the third, philosophical, contends that moral responsibility can and should be founded transcendently out of socio-historical context. On the contrary, I affirm that moral responsibility is a social phenomenon, and that it is impossible to found or justify any "truth" independently of social contexts, because truth is a synonym of collective representation. I do not consider what one ought to be or to do, but what one is, and what one does effectively.