In both cases, a challenge to the established classification is brought under control by some theory of attendant harm. (Pg.98)
The book proceeds by developing two themes. One presents taboo as a spontaneous device for protecting the distinctive categories of the universe. Taboo protects the local consensus on how the world is organised. It shores up wavering certainty. It reduces intellectual and social disorder. We may well ask why is it necessary to protect the primary distinctions of the universe, and why are taboos so bizarre?
The second theme answers this with reflections on the cognitive discomfort caused by ambiguity. Ambiguous things can seem very threatening. Taboo confronts the ambiguous and shunts it into the category of the sacred. (Pg.94)
The concept of dirt makes a bridge between our own contemporary culture and those other cultures where behaviour that blurs the great classifications of the universe is tabooed. We denounce it by calling it dirty and dangerous; they taboo it. (Pg.98)