Thus, the prison in fact succeeds. It creates a form of illegality amongst others, which it isolates and organizes as the enclosed world of delinquency. Delinquency is not the most virulent illegality, but rather an effect of penality that makes it possible to supervise illegality. Prison has succeeded extremely well in producing delinquency, a politically and economically less dangerous form of illegality which can be isolated from other offenses. It is so successful that it has survived after 150 years of failures.
Why does prison create the delinquency that it is supposed to combat? There are certain advantages to delinquency: one) delinquency can be supervised because delinquents are a small group; two) it can be directed to other activities and separated from the main group; three) it may be useful in colonization projects; four) delinquents have political uses as informers.
But the organization of delinquency would be impossible without organized police surveillance. Through supervising delinquency, one can control the whole social field. Surveillance works only together with the prison, which creates an organization of delinquency. Prison and the police together create an enclosed world of delinquency. Each part of the system supports another. Unsuccessful attempts were made to separate delinquents from the lower classes. A polemic took place in the workers' press about crime and penality; nineteenth century anarchists attempted to disengage delinquency from bourgeois illegality and legality. They attempted to reestablish the political unity of popular illegalities.
A key theme here is the failure of prison as a remedy. Common sense might see the history of the prison in terms of its establishment, failure and attempts at reform. One could consider the prison as an institution that developed along a straight line. Foucault rejects this model in favor of something like a circle: a system in which one stage follows another perpetually. Every element of the system is unchanging; it is also perfect in its own way. Criticism of the prison for failing to reform delinquency misses the point, Foucault argues, because the carceral system aims to reorganize knowledge about crime, not eliminate it.
Prison, like the psychiatric hospital, marks out and isolates the "abnormal" or illegal elements of society. In doing this it "creates" something that can be controlled and which the state can put to various uses. Foucault does not argue that prison creates crime, merely that without prisons, crime and the criminal would be perceived in different ways. The prison is an essential building block of society. Removing it without changing anything else would not work.
The explanation that Foucault gives for the rise and continued existence of the carceral system centers on illegality:a range of popular behaviors that evade or fall outside the law. Foucault previously analyzed the eighteenth century shift towards a popular illegality of goods. The nineteenth century saw a development of this trend: a move from an illegality centered on property towards political illegality. Foucault is thinking of a shift from peasants stealing chickens and burning their landlords' houses to the widespread political activity of the French Revolution or the European revolutions of 1848. This is an interesting but problematic theory. Political uprisings in general were not the invention of the nineteenth century. However, if they are seen in terms of conflict between social classes, Foucault may have a point.