Purity and Kashrut Deborah Williger The dialectic of impurity is expressed by the old German proverb Dreck macht Speck, meaning “filth makes bacon.” This sounds like a non‐kosher introduction to the topic at hand, but the proverb articulates that children, like piglets, will put on weight once they ingest a certain amount of filth from their environment. This absorption increases the variety of intestinal germ population, which has been demonstrated to promote robust growth. On the other hand, there is the saying Vor dem Essen, Händewaschen nicht vergessen, warning “don't forget to wash your hands before you eat.” This claims the opposite: Certain impurities cause dangerous illnesses. Therefore, it is necessary to cleanse dirt that could be harmful and pose a risk to health and life. Infiltration by impurities must be prevented before they do damage. Both physical and psychological contaminations can affect individuals or groups. Spiritual contaminations that dominate one's entire existence fall, following traditional Jewish interpretations, into the category of idolatry. Worshiping foreign gods is a capital crime. The transgression of the commandment against making images, represented in the Hebrew Bible as the dance around the golden calf, is considered unthinkable. Measuring degrees of spiritual pollution seems impossible. By contrast, the natural sciences have no problem quantifying the exact doses and potential costs and benefits of pollution in a variety of environments. Once a critical mass of impurity enters a living organism, it can do harm. If the infected organic mass cannot be healed, it dies. The creatures’ organic mass disintegrates into its molecular units, and its bare skeletal remains emerge clean and purified. In the end, death makes a clean separation between organic and inorganic matter, while life presupposes the commingling of both unconditionally. Living organisms are characterized by diversity and movement. Organic and inorganic elements exchange, mix, mingle, and separate in rhythmic cycles. There is constant metabolic exchange between chemical elements, such as nitrogen, oxygen, and carbon; mineral building blocks, such as phosphorus, calcium, or iron; and various organic components, such as carbohydrates, enzymes, hormones, and amino acids in tissues, vessels, organs, and cellular nuclei. Living organisms, whether single or composite cell organisms, constantly establish a fluid equilibrium between internal and external elements. Life flourishes where separation and recombination, division, and fertilization occur. Once certain parts no longer come together in order to multiply, distances widen and borders emerge that eventually lead to permanent divisions, and life ends. It seems high time to develop new methods for cleansing and healing. Despite considerable scientific progress in the development of tools and technologies, all the way to computers and artificial intelligence, humanity has not succeeded in creating a more just and happier world. We continue to inflict poisonous ideologies, such as antisemitism, racism, and exploitation on each other, despite our technological progress and intellectual prowess. Furthermore, the evolution of human civilization has created unintended side effects, including population growth and mass production and consumption, as well as increasing levels of pollution that threaten the planet. The greatest threats emanate from the smallest particles, especially the waste products of nuclear fission. Radioactive and other forms of environmental pollution are postmodern forms of original sin that implicates all descendants in the future who did not commit the original offense. As this enormous mass of guilt piles up, what are the possibilities for expiation and atonement? Will there even be a possibility for reconciliation so that life will continue on earth? We do know that neither systemic nor individual violence can be purified by tears. That requires action. There is no point in waiting passively for redemption, as if a redeemer (a man) could arrive to undo the consequences of environmental pollution. The Jewish tradition is focused on right action. According to the Torah, one should never expect metaphysical interventions or the entry of divine forces into earthly affairs. Purification is a means of defense. For spiritual or physical hygiene, the following cleansing agents are available: reconciliation, teshuvah, time, water, sand, salt, and the medical arts. These different detergents have varying degrees of efficiency. In vain, Lady Macbeth tried to wash her hands to regain innocence. The success of purification depends on the manner and form of...