The purpose of Book III is to observe the various exceptional cases that do not neatly align with the theories delineated in Book I and defended in Book II. Durkheim dubs these “pathological” cases, reprising his use of biological terms to explain social phenomenon. He firmly believes that a scrutiny of deviant cases will not only reinforce his theory, but will enhance people’s understanding of the laws guiding the normal development of the division of labor. Criminal professions are the notable exception: They are not the result of the division of labor, but of differentiation. They contribute to variety but do not help the survival of the organism, the same way cancer increases the type of cell tissues but can be harmful to survival. Durkheim lists three exceptional social forms that most often reoccur. He explores each of them in turn in the following chapters.

The first form, covered in Chapter 1, are instances in which the division of labor do not give rise to organic solidarity. This is the case of commercial or industrial crises, which occur more frequently in “advanced” societies, indicating that organic solidarity, even when already formed, can disintegrate.