The beginning of this section is typical of Foucault: he characteristically began his works with a shocking image to attract the reader's attention. The horror of Damiens's 1757 execution shows that this is an unusual kind of history book. Foucault draws heavily on contemporary documents, like the two at the beginning, but goes beyond this to construct a complicated theoretical argument. This argument will chart the movement between the public execution and the modern prison.
The body-soul shift is central to Discipline and Punish. For Foucault, the body has a real existence, but the "modern soul" is a recent invention. There are limits to how you can punish the body, as the execution at the beginning demonstrates, but the soul allows new possibilities. Firstly, it allows you to consider why the crime occurred; the motives that drive the criminal become knowable, and the subject of investigation. Secondly, it becomes possible to consider the criminal beyond the crime and its punishment. Instead of inflicting a painful penalty, or killing him, it becomes possible to supervise and investigate him. The shift from body to soul also marks the end of the public idea of punishment, because whilst the body has to be tortured in public, the soul is a private thing.
Foucault's idea of the fragmentation of judgment is related to the shift away from the body. When a criminal is condemned to be executed, the judge alone passes the sentence. When he is sent to prison, he is also evaluated by doctors and psychiatrists. The rise of what Foucault calls the human sciences is a personal preoccupation, found throughout his work. Psychiatry, social work, medicine and other professions assess and judge people according to standards called norms: they ultimately decide what is "normal" and "abnormal". This involves judging not a crime but a person, making decisions about his sanity, his treatment, and even when he should be released. According to Foucault, the modern world has given the important power to judge to a shadowy body of professionals whose role is sometimes uncertain.
This section is also an introduction to Foucault's methodology. The reference to genealogy is vitally important here. It represents the idea of writing a history that reveals struggles, discontinuities and the role of the individual. Discourses such as that of modern punishment define what it is possible to say and do about certain things. People are in a sense trapped inside them, but Foucault aims to give them a voice and help them to resist. In Discipline and Punish, he writes in order free prisoners not from their cells but from the discourses that helped to create them. His argument is that when the power to judge shifted to a judgment about normal and abnormal, the modern soul was formed. The prisoner or delinquent with an abnormal soul is defined against the normal majority. In showing how the prisoner is oppressed, Foucault wants to show us what is wrong with the modern soul in general.
Of the four straightforward rules for this investigation, the fourth is the most interesting. The techniques applied to the prisoner and our attitudes to him show the ways in which power operates in society. The knowledge possessed by prison warders and psychiatrists creates a certain "technology of power." Foucault's metaphors are drawn from science and industry, but he is also clear that economic and social circumstances are important. The reference to systems of production (the means of making and creating products and capital) is from Marx.
Foucault's discussion of power is central to Discipline and Punish. He thinks that power is a strategy, or a game not consciously played by individuals but one that operates within the machinery of society. Power affects everyone, from the prisoner to the prison guard, but no one individual can "control" it.