 By historicizing the body, Foucault’s genealogies also have distinctive philosophical implications. They question the naturalistic explanatory framework that understands human nature—uncovered by science—as the basis for such complex areas of behavior as sexuality, insanity or criminality. A key idea in Foucault’s historical analysis of the modern penal institutions is that they operate with markedly different rationality than those that are aimed solely at retribution through pain. He effectively reveals the double role of the present system: it aims at both punishing and correcting, and therefore it mixes juridical and scientific practices. Foucault argued that the intervention of criminal psychiatry in the field of law that occurred at the beginning of the nineteenth century, for example, was part of the gradual shift in penal practice from a focus on the crime to a focus on the criminal, from the action to agency and personality. The new idea of the “dangerous individual” referred to the danger potentially inherent in the criminal person. The new rationality could not function in an effective way in the existing system without the emergence of new forms of scientific knowledge such as criminal psychiatry that enabled the characterization of criminals in themselves, beneath their acts. Foucault suggests that this shift resulted in the emergence of new, insidious forms of domination and violence. The critical impact of Discipline and Punish thus lies in its ability to reveal the processes of subject formation that operate in modern penal institutions. The modern prison does not just punish by depriving its inmates of liberty, it categorizes them as delinquent subjects, types of people with a dangerous, criminal nature.