“May it suffice to say that the prohibitions on unclean animals are not based on abhorrence but are part of an elaborate intellectual structure of rules that mirror God's covenant with his people.”

This quote has to do with Douglas’s interpretation of the ancient Jewish dietary regulations in the Book of Leviticus. Her interpretation includes the idea that prohibitions of certain animals are neither irrational, as sometimes assumed, nor based on their inherent “uncleanness,” but are part of a symbolic structure of belief and action that represents the relationship of the Jews and God. In the Preface, she goes so far as to argue that the prohibitions actually express the idea that it is abominable to harm the animals in question.

“In this book I have tried to show that rituals of purity and impurity create unity in experience. So far from being aberrations from the central project of religion, they are positive contributions to atonement.”

One of the aims of Douglas’s book is to dispute certain views of earlier anthropologists, including the view that purity rules represent a “primitive” (in the pejorative sense) pre-rational mindset. On the contrary, Douglas finds them tied to universal human religious feelings and perceptions, especially those related to making reparation for sin. By performing a sacrificial ritual, one can atone for an offense against the moral law.

“For I believe that ideas about separating, purifying, demarcating and punishing transgressions have as their main function to impose system on an inherently untidy experience.”

For Douglas, purity rituals and beliefs are fundamentally about order and disorder. They are a way to make sense out of human life, which can seem messy and chaotic. Therefore, they include an element of rational classification, with items that don't belong being excluded.