Mary Douglas is an outstanding example of an evaluative thinker at work. In Purity and Danger: An Analysis of Concepts of Pollution and Taboo, she delves in great detail into existing arguments that portray traditional societies as "evolving" from "savage" beliefs in magic, to religion, to modern science, then explains why she believes those arguments are wrong. She also adeptly chaperones readers through a vast amount of data, from firsthand research in the Congo to close readings of the Old Testament, and analyzes it in depth to provide evidence that traditional and Western religions have more in common than the first comparative religion scholars and early anthropologists thought. First evaluating her scholarly predecessors by marshalling their arguments, Douglas identifies their main weakness: that they dismiss traditional societies and their religions by identifying their practices as "magic," thereby creating a chasm between savages who believe in magic and sophisticates who practice religion.

One of the most widely read books in the social sciences, Purity and Danger established Mary Douglas as one of the twentieth century's leading social scientists. She delves in great detail into existing arguments that portray traditional societies as "evolving¿ from "savage¿ beliefsandexplains why she believes those arguments are wrong.