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 Defilement is never an isolated event. It
cannot occur except in view of a systematic ordering of ideas. Hence any
piecemeal interpretation of the pollution rules of another culture is bound to
fail. For the only way in which pollution ideas make sense is in reference to a
total structure of thought whose key-stone, boundaries, margins and internal
lines are held in relation by rituals of separation.
To illustrate this I take a hoary old puzzle from biblical scholarship, the abominations of Leviticus, and particularly the dietary rules. Why should the cannel, the hare and the rock badger be unclean? Why should some locusts, but not all, be unclean? Why should the frog be clean and the mouse and the hippopotamus unclean? What have chameleons, moles and crocodiles got in common that they should be listed together (Lev 11:27)?
To help follow the argument I first quote the relevant versions of Leviticus and Deuteronomy using the text of the new Revised Standard Translation.
3. You shall not eat any abominable things. 4. These are the animals you may eat: the ox, the sheep, the goat, 5. the hart, the gazelle, the roe-buck, the wild goat, the ibex, the antelope and the mountain-sheep. 6. Every animal that parts the hoof and has the hoof cloven in two, and chews the cud, among the animals you may eat. 7. Yet of those that chew the cud or have the hoof cloven you shall not eat these: The camel, the hare and  the rock badger, because they chew the cud but do not part the hoof, are unclean for you. 8. And the swine, because it parts the hoof MI but does not chew the cud, is unclean for you. Their flesh you shall not eat, and their carcasses you shall not touch. 9. Of all that are in the waters you may eat these: whatever has fins and scales you may eat. 10. And whatever does not have fins and scales you shall not eat; it is unclean for you. 11. You may eat all clean birds. 12. But these are the ones which you shall not eat: the eagle, the vulture, the osprey, 13. the buzzard, the kite, after their kinds; 14. every raven after its kind; 15. the ostrich, the night hawk, the sea gull, the hawk, after their kinds; 16. the little owl and the great owl, the water hen 17. and the pelican, the carrion vulture and the cormorant, 18. the stork, the heron, after their kinds; the hoopoe and the bat. 19. And all winged insects are unclean for you; they shall not be eaten. 20. All clean winged things you may eat.
2. These are the living things which you may eat among all the beasts that are on the earth. 3. Whatever parts the hoof and is cloven-footed and chews the cud, among the animals you may eat. 4. Nevertheless among those that chew the cud or part the hoof, you shall not eat these: The camel, because it chews the cud but does not part the hoof, is unclean to you. 5. And the rock badger, because it chews the cud but does not part the hoof, is unclean to you. 6. And the hare, because it chews the cud but does not part the hoof, is unclean to you. 7. And the swine, because it parts the hoof and is cloven-footed but does not chew the cud, is unclean to you. 8. Of their flesh you shall not eat, and their carcasses you shall not touch; they are unclean to you. 9. These you may eat of all that are in the waters. Everything in the waters that has fins and scales, whether in the seas or in the rivers, you may eat. 10. But anything in the seas or the rivers that has not fins and scales, of the swarming creatures in the waters and of the living creatures that are in the waters, is an abomination to you. 11. They shall remain an abomination to you; of their flesh you shall not eat, and their carcasses you shall have in abomination. 12. Everything in the waters that has not fins and scales is an abomination to you. 13. And these you shall have in abomination among the birds, they shall not be eaten, they are an abomination: the eagle, the ossifrage, the osprey, 14. the kite, the falcon according to its kind, 15. every raven according to its kind, 16. the ostrich and the night hawk, the seagull, the hawk according to its kind, 17. the owl, the cormorant, the ibis, 18. the water hen, the pelican, the vulture, 19. the stork, the heron according to its kind, the hoopoe and the bat. 20. All winged insects that go upon all fours are an abomination to you. 21. Yet among the winged insects that go on all fours you may eat those which have legs above their feet, with which  to leap upon the earth. 22. Of them you may eat: the locust according to its kind, the bald locust according to its kind, the cricket according to its kind, and the grasshopper according to its kind. 23. But all other winged insects which have four feet are an abomination to you. 24. And by these you shall become unclean; whoever touches their carcass shall be unclean until the evening, 25. and whoever carries any part of their carcass shall wash his clothes and be unclean until the evening. 26. Every animal which parts the hoof but is not cloven-footed or does not chew the cud is unclean to you: everyone who touches them shall be unclean. 27. And all that go on their paws, among the animals that go on all fours, are unclean to you; whoever touches their carcass shall be unclean until the evening, 28. and he who carries their carcass shall wash his clothes and be unclean until the evening; they are unclean to you. 29. And these are unclean to you among the swarming things that swarm upon the earth; the weasel, the mouse, the great lizard according to its kind, 30. the gecko, the land crocodile, the lizard, the sand lizard and the chameleon. 31. These are unclean to you among all that swarm; whoever touches them when they are dead shall be unclean until the evening. 32. And anything upon which any of them falls when they are dead shall be unclean. 41. Every swarming thing that swarms upon the earth is an abomination; it shall not be eaten. 42. Whatever goes on its belly, and whatever goes on all fours, or whatever has many feet, all the swarming things that swarm upon the earth, you shall not eat; for they are an abomination.All the interpretations given so far fall into one of two groups: either the rules are meaningless, arbitrary because their intent is disciplinary and not doctrinal, or they are allegories of virtues and vices. Adopting the view that religious prescriptions are largely devoid of symbolism, Maimonides said:
The Law that sacrifices should be brought is evidently of great use . . . but we cannot say why one offering should be a lamb whilst another is a ram, and why a fixed number of these should be brought. Those who trouble themselves to find a cause for any of these detailed rules are in my eyes devoid of sense .... [Friedlander, trans. 1885]As a mediaeval doctor of medicine, Maimonides was also disposed to believe that the dietary rules had a sound physiological basis, but we have already dismissed in the second chapter [not reprinted here] the medical approach to symbolism. For a modern version of the view that the dietary rules are not symbolic, but ethical, disciplinary, see Epstein's English notes to the Babylonian Talmud and also his popular history of Judaism (1959: 24):
Both sets of laws have one common aim . . . Holiness. While the positive precepts have been ordained for the cultivation of virtue, and for the promotion of those finer qualities which distinguish the truly religious and ethical being, the negative precepts arc defined to combat vice and suppress other evil tendencies and instincts which stand athwart man's striving towards holiness .... The negative religious laws are likewise assigned educational aims and purposes. Foremost among these is the prohibition of eating the flesh of certain animals classed as "unclean." This law has nothing totemic about it. It is expressly associated in Scripture with the ideal of holiness. Its real object is to train the Israelite in selfcontrol as the indispensable first step for the attainment of holiness.According to Professor Stein's "The Dietary Laws in Rabbinic and Patristic Literature" , the ethical interpretation goes back to the time of Alexander the Great and the Hellenic influence on Jewish culture. The first century A.D. Letter of Aristeas teaches that not only arc the Mosaic rules a valuable discipline which "prevent[s] the Jews from thoughtless action and injustice," but they also coincide with what natural reason would dictate for achieving the good life. So the Hellenic influence allows the medical and ethical interpretations to run together. Philo held that Moses' principle of selection was precisely to choose the most delicious meats:
The lawgiver sternly forbade all animals of land, sea or air whose flesh is the finest and fattest, like that of pigs and scaleless fish, knowing that they set a trap for the most slavish of senses, the taste, and that they produced gluttony [Special Laws 4.100]],(and here we are led straight into the medical interpretation):
an evil dangerous to both soul and body, for gluttony begets indigestion, which is the source of all illnesses and infirmities.In another stream of interpretation, following the tradition of Robertson Smith and Frazer, the Anglo-Saxon Old Testament scholars have tended to say simply that the rules arc arbitrary because they are irrational. For example, Nathaniel Micklem  says:
Commentators used to give much space to a discussion of the question why such and such creatures, or such arid such states and symptoms were unclean. Have we, for instance, primitive rules of hygiene? Or were certain creatures and states unclean because they represented or typified certain sins? 1t may be taken as certain that neither hygiene, nor any kind of typology, is the basis of uncleanness. These regulations  are not by any means to be rationalised. Their origins may be diverse, and go back beyond history ....Compare also S. R. Driver (1895):
The principle, however, determining the line of demarcation between clean animals and unclean, is not stated; and what it is has been much debated. No single principle, embracing all the cases, seems yet to have been found, and not improbably more principles than one cooperated. Some animals may have been prohibited on account of their repulsive appearance or uncleanly habits, others upon sanitary grounds; in other cases, again, the motive of the prohibition may very probably have been a religious one, particularly animals may have been supposed, like the serpent in Arabia, to be animated by superhuman or demoniac beings, or they may have had a sacramental significance in the heathen rites of other nations; and the prohibition may have been intended as a protest against these beliefs ....P. P. Saydon takes the same line in the Catholic Commentary on Holy Scripture (1953), acknowledging his debt to Driver and to Robertson Smith. It would seem that when Robertson Smith applied the ideas of primitive, irrational and unexplainable to some parts of Hebrew religion they remained thus labelled and unexamined to this day.
Chapters xi to xv are perhaps the least attractive in the whole Bible. To the modern reader there is much in them that is meaningless or repulsive. They are concerned with ritual "uncleanness" in respect of animals (11), of childbirth (12), skin diseases and stained garments (13), of the rites for the purgation of skin diseases (14), of leprosy and of various issues or secretions of the human body (15). Of what interest can such subjects be except to the anthropologist? What can all this have to do with religion?Pfeiffer's general position is to be critical of the priestly and legal elements in the life of Israel. So he too lends his authority to the view that the rules in the Priestly Code are largely arbitrary:
Only priests who were lawyers could have conceived of religion as a theocracy regulated by a divine law fixing exactly, and therefore arbitrarily-, the sacred obligations of the people to their God. They thus sanctified the external, obliterated from religion both the ethical ideals of Amos and the tender emotions of Hosea, and reduced the Universal Creator  to the stature of an inflexible despot .... From immemorial custom P derived the two fundamental notions which characterise its legislation: physical holiness and arbitrary enactment-archaic conceptions which the reforming prophets had discarded in favour of spiritual holiness and moral law [Pfeiffer 1957: 91].It may be true that lawyers tend to think in precise and codified forms. But is it plausible to argue that they tend to codify sheer nonsense - arbitrary enactments? Pfeiffer tries to have it both ways, insisting on the legalistic rigidity of the priestly authors and pointing to the lack of order in the setting out of the chapter to justify his view that the rules are arbitrary. Arbitrariness is a decidedly unexpected quality to find in Leviticus, as the Rev. Prof. H. J. Richards has pointed out to me. For source criticism attributes Leviticus to the Priestly source, the dominant concern of whose authors was for order. So the weight of source criticism supports us in looking for another interpretation.
admits that most people find the biblical food restrictions not understandable. If God is the Creator of everything, why should His law be so severe as to exclude some animals even from touch (128f.)? His first answer still links the dietary restrictions with the danger of idolatry .... The second answer attempts to refute specific charges by means of allegorical exegesis. Each law about forbidden foods has its deep reason. Moses did not enumerate the mouse or the weasel out of a special consideration for them (143f.). On the contrary, mice are particularly obnoxious because of their destructiveness, and weasels, the very symbol of malicious tale-bearing, conceive through the ear and give birth through the mouth (164f.). Rather have these holy laws been given for the sake of justice to awaken in us devout thoughts and to form our character (161-168). The birds, for instance, the Jews arc allowed to eat are all tame and clean, as they live by corn only. Not so the wild and carnivorous birds who fall upon lambs and goats, and even human beings. Moses, by calling the latter unclean, admonished the faithful not to do violence to the weak and not to trust their own power (145-148). Cloven-hoofed animals which part their hooves symbolise that all our actions must betray proper ethical distinction and be directed towards righteousness .... Chewing the cud, on the other hand stands for memory.Professor Stein goes on to quote Philo's use of allegory to interpret the dietary rules: 
Fish with fins and scales, admitted by the law, symbolise endurance and self-control, whilst the forbidden ones are swept away by the current, unable to resist the force of the stream. Reptiles, wriggling along by trailing their belly, signify persons who devote themselves to their ever greedy desires and passions. Creeping things, however, which have legs above their feet, so that they can leap, are clean because they symbolise the success of moral efforts.Christian teaching has readily followed the allegorising tradition. The first century epistle of Barnabas, written to convince the Jews that their law had found its fulfilment, took the clean and unclean animals to refer to various types of men, leprosy to mean sin, etc. A more recent example of this tradition is in Bishop Challoner's notes on the Westminster Bible in the beginning of this century:
Hoof divided and cheweth the cud. The dividing of the hoof and chewing of the cud signify discretion between good and evil, and meditating on the law of God; and where either of these is wanting, man is unclean. In like manner fishes were reputed unclean that had not fins and scales: that is souls that did not raise themselves up by prayer and cover themselves with the scales of virtue. (Footnote verse 3)These are not so much interpretations as pious commentaries. They fail as interpretations because they are neither consistent nor comprehensive. A different explanation has to be developed for each animal and there is no end to the number of possible explanations.
But if you will not obey the voice of the Lord your God or be careful to do all his commandments and his statutes which I command you this day, then all these curses shall come upon you and overtake you. Cursed shall you be in the city, and cursed shall you in the field. Cursed shall be your basket and your kneading trough. Cursed shall be the fruit of your body, and the fruit of your ground, the increase of your cattle, and the young of your flock. Cursed shall you be when you come in and cursed shall you be when you go out. The Lord will send upon you curses, confusion, and frustration in all that you undertake to do, until you are destroyed and perish quickly on account of the evil of your doings, because you have forsaken me .... The Lord will smite you with consumption, and with fever, inflammation, and fiery heat, and with drought, and with blasting and with mildew; they shall pursue you till you perish. And the heavens over your head shall be brass and the earth under you shall be iron. The Lord will make the rain of your land powder and dust; from heaven it shall come down upon you until you are destroyed. (Deut 28:15-24)From this it is clear that the positive and negative precepts are held to be efficacious and not merely expressive: observing them draws down prosperity, infringing them brings danger. We are thus entitled to treat them in the same way as we treat primitive ritual avoidances whose breach unleashes danger to men. The precepts and ceremonies alike are focussed on the idea of the holiness of God which then must create in their own lives. So this is a universe in which men prosper by conforming to holiness and perish when they deviate from it. If there were no other clues we should be able to find out the Hebrew idea of the holy by examining the precepts by which men conform to it. It is evidently not goodness in the sense of an all-embracing humane kindness. Justice and moral goodness may well illustrate holiness and form part of it, but holiness embraces other ideas as well.
17. Say to Aaron, None of your descendants throughout their generations who has a blemish may approach to offer the bread of his God. 18. For no one who has a blemish shall draw near, a man blind or lame, or one who has a mutilated face or a limb too long, 19. or a man who has au injured foot or an injured hand, 20. or a hunch-back, or a dwarf, or a man with a defect in his sight or an itching disease or scabs, or crushed testicles; 21. no man of the descendants of Aaron the priest who has a blemish shall come near to offer the Lord's offerings by fire; . . .In other words, he must be perfect as a man, if he is to be a priest.
5. What man is there that has built a new house and has not dedicated it? Let him go back to his house, lest he die in the battle and another man dedicate it. 6. What man is there that has planted a vineyard and has not enjoyed its fruit? Let him go back to his house, lest be (lie in the battle and another man enjoy its fruit. 7. And what man is there that has betrothed a wife and has not taken her? Let him go back to his house, lest he die in the battle and another mail take her.Admittedly there is no suggestion that this rule implies defilement. It is not said that a man with a half-finished project on his hands is defiled in the same way that a leper is defiled. The next verse in fact goes on to say that fearful and faint-hearted men should go home lest they spread their fears. But there is a strong suggestion in other passages that a man should not put his hand to the plough and then turn back. Pedersen goes so far as to say that:
in all these cases a man has started a new important undertaking without having finished it yet . . . a new totality has come into existence. To make a breach in this prematurely, i.e. before it has attained maturity or has been finished, involves a serious risk of sin (Vol. 3, p. 9).If we follow Pedersen, then blessing and success in war required a man to be whole in body, whole-hearted and trailing no uncompleted schemes. There is an echo of this actual passage in the New Testament parable of the man who gave a great feast and whose invited guests incurred his anger by making excuses (Luke 14:16-24; Matthew 22. See Black and Rowley 1962: 836). One of the guests had bought a new farm, one had bought ten oxen and had not yet tried them, and one had married a wife. If according to the old Law each could have validly justified his refusal by reference to Deuteronomy 20, the parable supports Pedersen's view that interruption of new projects was held to be bad in civil as well as military contexts.
23. And you shall not lie with any beast and defile yourself with it, neither shall any woman give herself to a beast to lie with it: it is perversion.The word `perversion' is a significant mistranslation of the rare Hebrew word tebel, which has as its meaning mixing or confusion. The same theme is taken up in Lev 19:19.
You shall keep my statutes. You shall not let your cattle breed with a different kind; you shall not sow your field with two kinds of seed; nor shall there come upon you a garment of cloth made of two kinds of stuff.All these injunctions are prefaced by the general command:
Be holy, for I am holy. We can conclude that holiness is exemplified by completeness. Holiness requires that individuals shall conform to the class to which they belong. And holiness requires that different classes of things shall not be confused.
For thou makest men like the fish of the sea, like crawling things that have no ruler. (1:14)The prototype and model of the swarming things is the worm. As fish belong in the sea so worms belong in the realm of the grave, with death and chaos.
18. You shall therefore lay up these words of mine in your heart and in your soul; and you shall bind them as a sign upon your hand, and they shall be as frontlets between your eyes. 19. And you shall teach them to your children, talking of them when you are sitting in your house, and when you are walking by the way, and when you lie down and when you rise. 20. And you shall write them upon the doorposts of your house and upon your gates.If the proposed interpretation of the forbidden animals is correct, the dietary laws would have been like signs which at every turn inspired meditation on the oneness, purity and completeness of God. By rules of avoidance, holiness was given a physical expression in every encounter with the animal kingdom and at every meal. Observance of the dietary rules would thus have been a meaningful part of the great liturgical act of recognition and worship which culminated in the sacrifice in the Temple.