Imprisonment has always been a technical project. The transition from public executions was a technical mutation. The replacement of chain-gangs by the police-carriage was symbolic of this. The chain-gang was a public spectacle, a traveling fair of crime linked to the tradition of public execution. A kind of mobile panopticon replaced the chain-gang. The panoptic carriage did not last long, but it shows the way in which penal detention centered on reform replaced public execution.

Prison is strangely denounced as a great failure of penal justice. Prisons do not follow a chronology of establishment—a recognition of failure and then reform. In fact the critique of prisons appeared early. It took various forms: one) Prisons do not diminish the crime rate; two) Detention causes recidivism three) Prison produces delinquents by its constraints and very environment; four) Prison encourages delinquents to associate and plot future crimes; five) Prison conditions and condemns freed inmates to future recidivism and later surveillance; six) Prisons produce delinquency by making the prisoner's family destitute.

Critics always argued that prison is not corrective enough, or that, in correcting, it loses its power of punishment. The answer is always the reactivation of penitentiary techniques. The recent (1972–4) prison riots in France have been blamed on the failure of the 1945 reforms. In fact, the key features of these reforms were unchanged for 150 years. They have seven universal maxims: one) detention must transform the individual's behavior; two) convicts must be isolated and distributed according to offense, age and stage of transformation; three) penalties should be tailored to the individual; four) work is an essential part of the transformation and socialization of convicts; five) the education of prisoners is necessary for them, and for society; six) the prison regime must be partly supervised by specialized staff; seven) imprisonment must be followed by supervision and assistance until the prisoner is rehabilitated.

The same fundamental principles are repeated age after age. We should not think of the prison, its failure and reform as three stages, but rather as a system imposed on the juridical deprivation of liberty. The system comprises the discipline of prison, increasing objectivity, the reintroduction of criminality and the repetition of reform. This is the carceral system. Failure is an essential part of the prison. The prison has survived for so long because the carceral system is deep-rooted and fulfills particular functions.

If prison is intended to reduce offenses, then it fails as an institution of repression. Perhaps we should ask what function failure serves. We should see the prison as distinguishing offenses rather than eliminating them. It provides illegalities with a certain economy. The general schema of late eighteenth century reform is related to a struggle against illegalities. The whole equilibrium of illegalities was disturbed. At the turn of the nineteenth century, the danger of new popular illegalities arose. This was divided into three processes: one) the development of a political dimension to popular illegality; two) the development of peasant illegality against a new regime of landed property; and three) criminality became more specialized. Diverse illegal practices came together to form a new threat.

Popular illegalities had three means of diffusion: one) their insertion into the general political outlook; two) the articulation of social struggles; three) the communication between different forms and levels of offenses. Although this was not fully developed, it bred fear of a criminal underclass among the administrators of society. This led to a certain polarization or class asymmetry, as the criminal class became identified with the lower orders.