Purity and pollution

Purity and pollution are among the most widely distributed religious categories, and the systems built on them govern food, bodies, contact, space and access to the sacred across a great many traditions.

The analytical breakthrough is Mary Douglas's Purity and Danger (1966), which argued that pollution beliefs are not primitive hygiene or irrational taboo but expressions of a culture's classificatory system. Her formula, that dirt is "matter out of place", holds that what pollutes is what falls between or violates a society's categories: shoes are not dirty in themselves, but they are dirty on the dining table. She applied this to the dietary laws of Leviticus 11, arguing that the forbidden animals are those failing to conform to the classification of their domain, creatures of the sea without fins and scales, land animals that do not both chew the cud and part the hoof, so that the abominable is the anomalous. Her reading has been extensively criticised and modified, including by Douglas herself in later work, but it transformed the subject by making pollution systems intelligible rather than merely strange.

The systems themselves vary enormously in what they treat as polluting, which is itself evidence for the classificatory account. Israelite and Jewish purity law concerns corpses, certain animals, skin disease, and genital discharges including menstruation and childbirth, and it regulated access to the Temple; after 70 CE much of it lapsed in practice, while parts persist, notably the laws of family purity and the mikveh. Hindu purity is bound to caste, to substances, to the body's boundaries and to death, and its role in sustaining caste hierarchy has made it politically central, B. R. Ambedkar's critique addressed it directly, and the Indian constitution abolishes untouchability by name. Islamic purity law is developed in fine detail as a precondition of prayer, with major and minor impurity and their respective ablutions. Shinto is organised around kegare, pollution, especially from death and blood, and harae, purification, which is the tradition's most characteristic ritual act. Zoroastrian purity law is exceptionally elaborate, and its treatment of corpse pollution, which forbids defiling earth, water or fire with a body, produced the practice of exposure.

Two general observations recur. Pollution is very often contagious and is removed by procedure rather than by intention, which distinguishes it from sin, one may be impure without having done anything wrong, though the two are frequently entangled in practice and in rhetoric. And purity systems disproportionately regulate women's bodies, a pattern documented across traditions and periods. Feminist scholarship has analysed this at length, and reform movements within several traditions have contested particular applications while retaining the wider framework.

Mary Douglas's account of pollution as classificatory disorder, "matter out of place," is the dominant reading article one presents, but it is not the only influential one, and biblical scholarship has since offered a different account of the same material she analysed.

Jacob Milgrom's commentaries on Leviticus argue that Israelite impurity centres on death and its symbolic associates, corpses, certain skin conditions, genital discharge, rather than on classificatory anomaly as such; on his reading the system is fundamentally about the opposition of life and death rather than about categories violated. Jonathan Klawans has pressed a further distinction Douglas's framework does not make: between ritual impurity, a natural and morally neutral state requiring only purification, and moral impurity, generated by acts such as bloodshed or idolatry that pollute the land itself and cannot be washed away by ritual means. The distinction matters because conflating the two, treating menstrual impurity and murder as the same kind of thing, is a common misreading these scholars were writing against.

Contemporary religious communities argue over the same material rather than only its academic interpretation. Orthodox Judaism retains the laws of family purity and mikveh observance largely intact; Reform and Reconstructionist Judaism have generally set the purity framework aside as inapplicable outside a functioning Temple, while some feminist theologians within more traditional communities have sought to reclaim and reinterpret mikveh practice rather than abandon it, arguing the framework can be redeemed from within rather than only inherited or discarded.