Reasons for kashrut

Why do we keep kosher?

Kosher sign metal

Maimonides holds that the Torah’s mitzvot are rational, and we’re permitted to ask what these reasons may be, even if we are not sure of what some of these reasons are. For Maimonides, the idea that God gave laws without reason is anathema.

Indeed, there are reasons for the laws of kashrut, but the most popular idea – hygiene – is incorrect. Isadore Grunfeld writes:

The laws of kashrut were once though to have been based on hygiene. It was believed by some that kosher animals were healthier for man to eat than non-kosher animals. It was also noted that the laws of purity (Leviticus 11-15) not only describe the difference between clean and unclean animals, but also describe other phenomenon related to health. Thus, it was natural for many to assume that all the laws of kashrut were merely hygenic in intent and origin. However, this idea has fallen out of favor among biblical scholars for a number of reasons.

Such a rationale is tenable if one only considers the laws prohibiting scavenger birds, which mat varry disease from the carrion they; the laws which forbid the consumption of shellfish, which can contain parasites which can harm people, and the laws prohibiting the consumption of pork, which can harbor trichinosis if not properly cooked. However, this hypothesis falls apart when one looks at the other laws of kashrut: They also forbid the consumption of birds of prey, which do not carry such diseases; they forbid the consumption of all fish without true scales, such as sharks. They even permit animals such as cows and sheep which we know can harbor diseases which are dangerous to humans. Other reasons that hygiene cannot be the primary motivation behind the laws is that this hypothesis does not explain the following parts of the Jewish dietary laws: Fruit from trees may not be eater before the tree turns four years old; One must remove all blood from the meat; Fruits and vegetables may be eaten without prohibition. Why not outlaw poisonous herbs, seeds, berries and fruits?

– Isadore Grunfeld, The Jewish Dietary Laws, 1972, vol. 2, p. 213

Why are the laws of kashrut the way that they are?

Concentric rings of holiness – an idea implied in various traditional Jewish commentaries, but stunningly described by Mary Douglas in her class work, Purity and Danger.

Parashat Ha-Shavua, Leviticus 9:1 – 11:47, April 25, 1998 – 29 Nisan 5758
Dr. Diane M. Sharon, Visiting Assistant Professor of Bible.

This week’s parashah is overflowing with mystery–first, in Leviticus 10, the sudden deaths of Aaron’s sons in the very midst of dedicating the Mishkan and the Aaronid priesthood to its service, and then, in chapter 11, the extensive categories of clean and unclean animals that may or may not be eaten. Both of these texts stand as a challenge to the notion of a rational religion, to the idea that God is reasonable, a divinity who may be predicted, and also to the idea that the way to worship God, the way to live a sacred life, is based on logical premises.

In spite of these challenges, the history of interpretation of this parashah shows a
striving for the rational. On the deaths of Aaron’s sons, Rashi cites rabbinic efforts to identify the sins that Nadab and Abihu must have committed that would warrant their incendiary punishment–these differ widely, emphasizing the elliptical nature of this text. And on the food prohibitions, Maimondies, known as Rambam, the twelth-century neo-classical philosopher who is known for his rational approach to Judaism, read into the food laws of Leviticus a logical underpinning based on sound hygiene.

Rambam’s intuition of a rational basis for the food laws in Leviticus 11 has been challenged, affirmed and rechallenged over the centuries, emphasizing the difficulty in finding clear cut rational premises in the biblical classification of clean and unclean animals. Mary Douglas, a structural anthropologist and student of Claude Levi-Strauss, is well known to modern biblical scholarship for her 1966 work Purity and Danger, in which she examines the food prohibitions in Leviticus 10 and Deuteronomy 14 from an anthropological perspective.

Douglas sees the food categories as inhabiting spheres of action set by God during the six days of creation, and consisting of creatures whose primary domain is water, earth, or air. She concludes in this classic analysis that the distinctions between clean and unclean animals are based on the principle that clean animals stay well within the boundaries of their particular habitat, but unclean animals somehow cross boundaries from one habitat to another, and are thereby perceived as threatening.

For example, the ideal inhabitant of water exhibits fins and scales. Creatures of the water that do not stay within this boundary, that do not exhibit fins and scales, are deemed unfit. Creatures that mainly inhabit the air must have feathers and wings. Winged creatures that can’t fly, or creatures of the air that do not have wings and feathers, blur the boundaries and are deemed unclean. Creatures that swarm on the earth are unclean. They must leap if they are insects (grasshoppers are okay), part the hoof and chew their cud if they are animals. The pig, camel, hyrax, hare and rock badger are
missing one or the other quality, and, because they blur boundaries, are considered unfit.

Douglas’s categories rely largely but not exclusively on the means of locomotion appropriate to each sphere. The scheme she extrapolates from the food prohibitions yields a series of concentric circles, with each larger boundary reinforcing the inner one, and each inner one enclosing yet another. Everything that seems eligible to violate any of the boundaries is segregated and put into a category of defilement.

…  I would like to summarize these briefly, and to conclude by suggesting ways Douglas’s analysis is relevant in our thinking about our religious circumstances today.

In her analysis of the Israelite attitudes towards anomalies, viewing as unclean those elements that cross or blur boundaries, Douglas concludes that here is a people who prefer their boundaries to remain intact. … For Israel, being holy means being set apart. The Israelites cherish their boundaries and want nothing better than to keep them strong and high. Creation in Genesis begins with distinctions between light and darkness, and concludes with the distinction between the six days of God’s work and the seventh of rest. At the end of Shabbat, during Havdalah (which means “to make distinctions”), Jews today still bless God who differentiates between the holy and profane, between light and darkness, between Israel and other nations, between Shabbat and the rest of the week.


“Purity and Danger: An Analysis of Concepts of Pollution and Taboo” is a 1966 book by the anthropologist and cultural theorist Mary Douglas. It is her best known work. In 1991 the Times Literary Supplement listed it as one of the hundred most influential non-fiction books published since 1945. It has gone through numerous reprints and re-editions. In 2003 a further edition was brought out as volume 2 in Mary Douglas: Collected Works. (Wikipedia)