What is the theme in Purity and Danger: An Analysis of Concepts of Pollution and Taboo by Mary Douglas?

Another theme in this book is religions. Douglas analyzes and tries to understand religions and uses them to gain understanding of the way concepts of pollution and taboo are understood by various cultures. To do this, she tries to get to the bottom of the essentials of religion while comparing various views about destiny and place in the universe. She considers that to do that it is important to confront our own ideas of contagion.