Douglas looks at several of the dietary rules of Leviticus, including prohibited animals such as the ox and pig and classifications of animals based on anatomy or motion. Douglas argues that these rules, arbitrary as they may seem, express the idea of wholeness in the body and in society, mirroring the covenant between the Jews and God. She theorizes that some of the prohibitions express the idea of certain animals being anomalous, or falling between categories of classification. For example, the Mosaic law deemed some birds unclean because they swam as well as flew, and thus were not entirely birdlike.