Kashrut

The circled U indicates that this can of tuna is certified kosher by the Union of Orthodox Congregations.

The laws of Kashrut (כשרות) ("keeping kosher") are the Jewish dietary laws. Food in accord with Jewish law is termed kosher, from the Hebrew term kasher (כשר), meaning "fit" (in this context, fit for human consumption). Food not in accord with Jewish law is termed treifah or treif (טרפה) ("torn"); the term originally referred to animals which had been slaughtered after being mortally wounded by wild beasts and therefore were not fit for human consumption. Among Sephardim it typically only refers to meat that is not kosher.

The basic laws of kashrut are in the Biblical book of Leviticus, their details explicated in the oral law (the Mishnah and the Talmud) and codified by the later rabbinical authorities.

There are actually varying degrees of Kashrut, with the ultimate degree shading into behavior more than just the food itself. For instance, meat which is not Kosher may be sold to the general public or used for pet food; however, milk and meat may not be combined together, even if the resulting mixture is to be discarded, let alone sold or fed to a pet.

Types of foods

Meat

Modern halakha on kashrut classifies the flesh of both mammals and birds as "meat"; fish however are considered to be 'parve' (פרווה), neither meat nor dairy.

Mammals

Kosher mammals must have two features; cloven hooves and chewing their cud. All kosher mammals are artiodactyl herbivores, such as domesticated cows, goats, or sheep, or wild deer, elk, etc.

Birds

Kosher birds include: duck (domestic), goose (domestic), chicken, capon (castrated rooster), turkey, guinea fowl and many others. As a general principle, scavenging birds such as vultures and birds of prey such as hawks and eagles (which will eat carrion when they find it) are not considered kosher, while other birds generally are. Leviticus outlines the non-kosher birds and the rest are all kosher; in practice, however, the identities of the birds listed as kosher are not all known, so religious authorities have restricted consumption to specific birds which Jews have traditionally eaten. Thus birds such as songbirds, which are consumed as delicacies in many societies, are not generally eaten although they might theoretically be Kosher.

Kosher slaughter and preparation

Jewish law states that kosher mammals and birds must be slaughtered according to a strict set of guidelines, the slaughter (shechita) (שחיטה) being designed to minimize the pain inflicted. This necessarily eliminates the practice of hunting wild game for food, unless it can be captured alive and ritually slaughtered.

A professional slaughterer, or shochet (שוחט), using a large razor-sharp knife with absolutely no irregularities, nicks or dents, makes a single cut across the throat to a precise depth, severing both carotid arteries, both jugular veins, both Vagus nerves, the trachea and the esophagus, no higher than the epiglottis and no lower than where cilia begin inside the trachea, causing instantaneous loss of blood flow to the brain and death in a few seconds. Any variation from this exact procedure could cause unnecessary suffering; therefore, if the knife catches even for a split second or is found afterward to have developed any irregularities, or the depth of cut is too deep or shallow, the carcass is not kosher (nevelah) and is sold as regular meat to the general public. The shochet must be not only rigorously trained in this procedure, but also a pious Jew of good character who observes the Sabbath, and who remains cognizant that these are God's creatures who are sacrificing their lives for the good of himself and his community and should not be allowed to suffer. In smaller communities, the shochet is often the town rabbi or the rabbi of one of the local synagogues; large factories which produce Kosher meat have professional full time shochets on staff.

Once killed, the animal is opened to determine whether there are any of seventy different irregularities or growths on its internal organs, which would render the animal non-kosher. The term "Glatt" kosher, although it is often used colloquially to mean "strictly kosher", properly refers to meat where the glatt (גלת) (lungs) are carefully examined for adhesions (i.e. scars from previous inflammation).

Large blood vessels must be removed, and all blood must be removed from the meat, as Jewish law prohibits the consumption of the blood of any animal. This is most commonly done by soaking and salting, but also can be done by broiling. An interesting fact, little-known outside of Jewish communities, is that the hindquarters of a mammal are not kosher unless the sciatic nerve and the fat surrounding it are removed (Genesis 32:33). This is a very time-consuming process demanding a great deal of special training, and is rarely done outside Israel, where there is a greater demand for kosher meat, since all meat sold in Jewish towns is required to be kosher by law. When it is not done, the hindquarters of the animal are sold for non-kosher meat.

Gelatin

A controversial topic is the status of gelatin. True gelatin consists of denatured proteins, and usually comes from the processed hides or bones of animals. If the source of gelatin is a kosher animal that was properly slaughtered according to Jewish law, or a kosher fish, then such gelatin is considered kosher by all Jews.

Another issue with gelatin is whether it is pareve. Kosher gelatin made from kosher fish is pareve. A kosher pareve 'gelatin' made from vegetable gums such as carrageenan combined with food starch from tapioca (which is also suitable for vegans) is commercially available in supermarkets which have substantial Kosher food sections. It does behave differently than protein-based gelatin, however, and cannot always be substituted directly for animal gelatin without modification of the recipe. Other gelatin-like materials available include combinations of carrageenan and other vegetable gums, such as guar gum, locust-bean gum, xanthan gun, gum acacia, and agar, chemically modified food starch, and chemically modified pectins. Recently, such products have come to be used in prepackaged gelled fruit products, where animal-based gelatin was previously used.

All other gelatin is usually considered treif (non-kosher). However, a number of prominent rabbinic authorities have noted that gelatin undergoes such extensive processing and chemical changes that it no longer has the status of meat, and as such may be considered pareve and kosher. Most Conservative Jews, and a significant minority of Israeli Orthodox Jews, accept that all gelatin is kosher.

This also affects the status of marshmallows, which contain gelatin as one of their principal ingredients.

Insects and other invertebrates, reptiles, and amphibians

With four exceptions, all insects and other invertebrates (including those usually consumed as seafood), all reptiles, and all amphibians are considered 'loathsome', 'crawling' creatures, and are forbidden as treif (un-kosher). The exceptions are a type of locust native to the Arabian peninsula, encompassing four distinct species. The tradition for identifying which species of locust were and were not kosher has been lost among all Jews except the Jews of Yemen. (One hypothesis links these kosher insects to the Biblical manna which was provided as food for the Israelites in the desert).

Bee honey is Kosher, even though bees are not, because the honey is made by the bee, not an excretion of the bee.

In the summer of 2004, a controversy arose in New York City over the presence of copepods (tiny crustaceans) in the city water supply. While some authorities hold that these creatures are microscopic and therefore negligible, others note that they are almost the size of a small insect, such as a gnat, and far larger than a bacterium or other single-celled creature; and in fact can be detected by the naked eye. As of this writing a definitive ruling has not been produced, but many families have begun using filters on their drinking and cooking water supply.

Dairy

Milk and milk-derived products derived from kosher animals are always kosher. All milk from cows, goats, and sheep is kosher. In practice, many Orthodox Jews use only "Cholov Yisroel" (חלב ישראל) milk and dairy products; this label means that the milk has been under constant rabbinical supervision from milking to bottling, to make sure that it is not admixed with the milk of a non-kosher animal. In the past, when milk from cows was more expensive, adulteration with camel milk or horse milk was a serious issue; today this is not considered a practical concern in the USA or in most western countries. As such, most Modern Orthodox rabbis and all Conservative rabbis hold that FDA supervision is sufficient for milk and dairy products to be considered automatically kosher.

Cheese

Cheese is, of course, considered a dairy product. Hard cheeses, however, are made from milk and rennet, an animal product, and the kashrut of such cheeses is a matter of debate in the religious Jewish community.

Rennet is the enzyme used to turn milk into curds and whey; most forms of rennet derive from the lining of the stomach of an animal. Kosher rennet may be made from the stomachs of kosher animals slaughtered in conformance with the laws of kashrut, or may be made from vegetable or microbial sources. The Mishna and Talmud (in Avodah Zarah and Hullin) state that cheese made with rennet derived from a non-kosher animal is non-kosher. Orthodox authorities follow this ruling, and hold that rennet is a "d'var ha'ma'amid" (דבר המאמעמיד), something that changes the status of the food so much that any amount makes the food it is added to non-kosher. Conservative authorities classify rennet as something that has changed so much from its original form that it is a "d'var chadash" (דבר חדש), "something new", and thus is no longer un-kosher. In practice Orthodox and some Conservative Jews eat only cheese made with kosher rennet, while other Conservative Jews follow the Conservative ruling and eat any hard cheese.

No mixing of meat and dairy

Milk products and meat products may not be eaten together in the same meal, much less cooked together. Jewish law thus mandates a set of 'fence' laws that prevent this from happening; cooking meat and milk together is prohibited, even if it is not eaten, eating milk and meat together is prohibited even if they are not cooked together, and no benefit can be attained from such activity; for instance, one cannot even serve meat and milk together to an animal. Note that this even applies to the flesh of birds, not just mammals. Jewish homes have two sets of silverware, cookware, cups, and dishes. One is for milk (Yiddish milchig, Hebrew halavi) dishes, and one is for meat (Yiddish fleishig, Hebrew basari) dishes. This prevents any trace of meat or dairy from being accidentally mixed. (Foods that contain neither milk nor meat are considered "neutral" -- Yiddish pareve, Hebrew parve.)

Jewish law considers glass (and some say Pyrex) to be non-absorbent; thus, one could use just a single set of glass plates and dishes. In practice, this is rarely done not only because of the cost, but also because it is held that it would weaken the traditional system of kashrut observance. However, it is common within most religiously observant households to allow drinking glasses to be used for both dairy and meat meals, as long as they are thoroughly washed.

Various customs are observed for how long it is necessary to wait after eating meat before eating dairy foods again. Most views hold that there is no wait needed to have meat soon after eating dairy, so long as the mouth is thoroughly cleaned. After eating meat, however, waits of three hours and six hours before consuming dairy products are the most common practices, though some communities wait only one hour (Dutch Jews).

Pareve

All foods which do not fall into the categories of meat or dairy are considered 'pareve' or neutral, and can be consumed freely with either meat or dairy. This includes all fruits and vegetables and foods derived exclusively from such sources; salt and other non-organic foodstuffs. Fish is considered pareve, and may be eaten directly before or after both meat and milk, but see Fish and Seafood below.

Produce

All fresh fruits and vegetables are kosher in principle. Jewish law requires that they be carefully checked and cleaned to make sure that there are no insects on them, as insects are not kosher (except certain Orthoptera, see above). In the last century emphasis on this aspect has increased, especially in the Haredi Jewish community. Many Haredim avoid certain vegetables, such as broccoli, because they may be infested and exceedingly hard to clean. Responding to this issue, some companies now sell thoroughly washed and inspected produce for those who do not wish to do it themselves, even going to the trouble of filtering the wash water to ensure that it carries no microscopic creatures (see discussion of such animals in tap water, above).

There are actually some restrictions on consumption of produce. The fruit of a tree for the first three years cannot be consumed (the law of orlah). For crops grown in the Holy Land, tithes must be taken and allocated according to the precepts of the Bible, otherwise the entire crop is not considered Kosher.

Grains and cereals

Unprocessed grains and cereals are kosher. Processed items (e.g. dry cereals, baked goods) may contain small quantities of non-kosher ingredients; therefore Orthodox Judaism holds that these goods should generally not be consumed unless there is a hechsher (mark of rabbinical certification of kashrut) on the product. Conservative Judaism often is more lenient, and holds that a careful reading of the ingredients is sufficient.

Kosher for Passover

During the 8 days of Passover there are additional restrictions on what foods may be eaten. Jewish law forbids Jews from eating any leavened product, and furthermore any product made from wheat, rye, barley, spelt, or oats (other than matzo, bread which has been ritually supervised from harvest to packaging to ensure that no leavening has occurred), which may have been inadvertently briefly moistened sometime after harvest, and begun the fermentation process which is key to leavening. Ashkenazic Jews are restricted from eating rice and legumes during Passover, while Sephardic Jews are permitted rice and typically legumes as well. In order to prevent inadvertent consumption of hometz, foods which are not Kosher for Passover, observant Jews maintain an entirely separate set of dishes, cutlery, pots, pans, etc. for Passover which can never be allowed to contact such foods, much as they maintain separate sets of such items for milk and for meat. Before Passover, the house is rigorously cleaned to eliminate any remnants of hometz, no matter how small. Many Jews who can afford it even maintain a separate kitchen for use during Passover, to eliminate the need for such a laborious procedure in their regular kitchen, with the risk of overlooking some nook or cranny somewhere where a crumb has lodged.

Fish and seafood

To be kosher, a fish must have both fins and scales. The lack of either characteristic renders that species of fish unkosher. Examples of unkosher fish include shark, catfish and eels. All shellfish, such as clams, oysters, crabs, lobster, and shrimp are not kosher. All sea mammals, such as dolphins, whales and seals are not kosher. All other sea animals, such as octopus, squid and jellyfish are also not kosher.

Seaweed and other sea plant life are all kosher.

The kashrut of swordfish and sturgeon are controversial, as they have scales as young fish, but lose them later in life. Orthodox authorities have ruled that these fish are not kosher, but many Conservative rabbis rule that they are kosher.

Fish is not considered to be meat, but rather neutral or 'pareve'; however, the laws of kashrut require fish and meat to be consumed separately. Unlike the separation between milk and meat, a separate set of dishes is not required, but dishes must be washed in between. Thus at a Sabbath meal, where traditionally there is a fish course and a meat course, there will always be a separate fish fork and fish plate, to avoid having the inconvenience of rinsing mid-meal. The Beth Yosef also forbids eating fish with dairy products; though most authorities attribute this to a printing error, some (particularly Sephardi Jews) follow this ruling.

Eggs

Eggs from kosher birds are kosher; they are also considered pareve (neutral, neither milk nor meat). Traditionally, eggs are examined in a glass cup to ascertain that they contain no blood. Partially-formed eggs found inside slaughtered birds may be eaten, but they must undergo the same process of blood removal as the animal, and these eggs are considered to be fleishig (status of meat).

Canned and frozen foods

Most such goods are usually permissible since manufacturers add only water and spices during the packaging process. Sometimes, however, fruits or vegetables are prepared with milk products or with non-kosher ingredients such as non-kosher meat broth. Orthodox Judaism thus holds that canned and frozen goods should generally not be consumed unless there is a hechsher (mark of rabbinical certification of kashrut) on the product. Conservative Judaism often is more lenient, and holds that a careful reading of the ingredients is sufficient.

Wine and grape products

Products made from grape juice, including wine, are only Kosher if produced by Jews. This is said to derive from the ritualistic religious use of wine by nonJews (as well as Jews); an entire vinyard, or an entire pressing of the grapes would be dedicated to a god other that that of the Jews, and if some of the product would find its way to be consumed by Jews, or even used for Kiddush, that would constitute idolatry or sacrilege. In order to provide a safety margin, all wine or grape juice from non-Jewish sources was therefore prohibited, even if it could be reasonably assumed to be free from such theological taint, and that prohibition continues to the present day.

Other

Questions of Kashrut also crop up regarding items which are not themselves consumed. For instance, production of aluminum foil requires the foil be squeezed between two rollers at tremendous pressure, to ensure constancy of thickness. Since the foil would retain toxic residue if it were lubricated with petroleum-based lubricants during this process, lubricants derived from animals or plants must be used. In the past, tallow or lard were often used, which would leave a residue on the foil rendering it nonkosher. However today, use of these products is economically unfavorable compared to use of vegetable-derived lubricants.

Vegetarianism

Since there are no laws of Kashrut restricting the consumption of plant products, it follows logically that a truly vegetarian meal would be inherently Kosher. In practice, however, those who rigorously follow the laws of Kashrut do not automatically regard all restaurants or prepared or canned food which claim to be vegetarian as Kosher, due to some doubt as to whether the degree of supervision maintained is in all cases sufficiently stringent. Many vegetarian restaurants and producers of vegetarian foods do acquire a hechsher, certifying that a Rabbinical organization has approved of them as Kosher, since this requires no additional care on their part if they are truly vegetarian.

The situation is not always reversible, however; although parve food can contain neither meat nor dairy, that label on a product cannot be always used by vegetarians as a reliable indication, since Kashrut considers fish to be parve. However, in practice it is rare to find fish products in parve foods; moreover, because of potential issues of mixing meat and fish (see #Fish_and_Seafood above) many Kashrut supervising authorities specifically indicate the presence of fish products when they are found in parve foods.

Genesis 1:29 states "And God said: Behold, I have given you every herb yielding seed which is upon the face of all the earth, and every tree that has seed-yielding fruit - to you it shall be for food." According to many classical Jewish Bible commentators, this means that God's original plan was for mankind to be vegetarian, and that God later gave permission for man to eat meat because of man's weak nature. However, others argue that people may eat animals because God gave Eve and Adam dominion over them. Few prominent rabbis have been vegetarian, a notable exception being the first Chief Rabbi of pre-state Israel, Abraham Isaac Kook.

Halakha strongly encourages the eating of meat at the Sabbath and Festival meals, and some Orthodox Jews who are otherwise vegetarian will nevertheless consume meat at these meals. Many Orthodox authorities have ruled that it is forbidden for an individual to become a vegetarian if they do so because they believe in animal rights; however, they have also ruled that vegetarianism is allowed for pragmatic reasons (if kosher meat is expensive or hard to come by in their area), health concerns, or for reasons of personal taste (if someone finds meat unpalatable).

Kashrut and animal welfare

The practice of kosher slaughter emphasizes the sharpness of the knife and the accuracy and precision of the skill of the shochet, in order to slit the jugular of the animal with an absolute minimum of pain and suffering. In general, over the years authorities have ruled that any unnecessary suffering by the animal can render otherwise kosher meat traife. Nevertheless, the method of slaughter used in strict adherence to Jewish law has been criticized as being inhumane by many animal rights organizations, in particular because animals are killed without the use of anesthesia, often administered to beef by firing a bolt into the brain or by electric shock to the head. (Traditional kashrut would often not allow for anesthesia, as it may severely injure the animal before it is slaughtered, rendering it Treifa, and because Kashrut prohibits slaughter of an unconscious animal.) This has resulted in several restrictions or even an outright ban on kosher meat in a number of countries, though other countries grant ritualistic slaughter such as kashrut special exemption from the relevant regulations. However, some bans were in place before animal rights had become a general public concern.

Animal rights groups claim it can take several minutes for the animal to die after kosher slaughter and thus would cause immense suffering. Jewish groups point to studies showing that the technique is no more painful than conventional techniques, and in most cases quicker and less painful; the emphasis on flawless procedure and tools contrasts with the often sloppy production line methodology of the slaughterhouse resulting in failure to stun the animal, as often described by animal rights advocates in other contexts. However, the conclusions of these studies are sometimes rejected by animal rights advocates. In addition, there are campaigns to have the practice of ritualistic slaughter globally banned.

In some ways, modern slaughtering practices and kashrut practices clash, although both may have good intentions with respect to hygiene and animal welfare; for instance, kashrut prohibits slaughter of an unconscious animal, for reasons of avoiding consumption of a diseased animal as well as the possibility of inhumane means of anesthesia, and relies on the skill of the shochet and the sharpness of the knife to slit the jugular as painlessly as possible. On the other hand, for reasons of hygiene, modern slaughterhouse regulations prohibit the carcass of an animal from falling into the blood of another, so that animals are often suspended by a leg before being slaughtered; they would normally be stunned by a blow to the head to prevent suffering in this process, but the prohibition of slaughter of an unconscious animal prevents this for kosher slaughter. Of course, other, more humane, methods of supporting the carcass of the animal after it is slaughtered are available, but since they are more expensive and not routinely used for nonkosher slaughter, slaughterhouses are reluctant to adopt them, and when they do often greatly raise the price of the meat to compensate for the nonstandard technique.

Many Jewish organizations suspect that covert anti-Semitism may also be an influence behind the efforts to ban kosher meat, partly because of a distinct anti-Semitic element among the opponents of ritualistic slaughter, partly because of the age of some bans.

Identification of kosher foods

Store-bought foods can be identified as kosher by the presence of a hechsher, a graphical symbol that indicates that the food has been certified as kosher by a rabbinic authority. The most common symbol is the "OU": a U inside a circle, standing for the Union of Orthodox Congregations. Each organization, however, has its own certification mark, and the other symbols are too numerous to list.

The hechsherim of certain authorities are sometimes considered invalid by certain other authorities. A solitary K is sometimes used as a symbol for kashrut, but as this symbol cannot be trademarked (the method by which other symbols are protected from misuse), it does not indicate anything other than the fact that the company producing the food considers it to be kosher.

Another way to check the kashrut of an item is to read the list of ingredients; however, many observers of kashrut do not consider this to be sufficient. It can, however, identify obviously unkosher substances present in food.

Producers of food items and food additives can contact Jewish authorities to have their product deemed kosher. A committee will visit their facilities to inspect production methods and contents of the product and issue a certificate if everything is in order.

For various reasons, such as changes in manufacturing processes, previously kosher products can 'lose their hechsher'; a change in lubricating oil to one containing tallow, for instance. In such cases, the supply of preprinted labels with the hechsher may still find its way onto the now nonkosher product; for such reasons, there is an active 'grapevine' among the Jewish community identifying with very little time lag which products are now questionable, as well as products which have become kosher but whose labels have yet to carry the hechsher.

Reasons for the Biblical dietary laws

There continues to be a debate on the purposes and meaning of the laws regarding Kashrut.

In Jewish philosophy it is recognised that of the 613 mitzvot, a large number cannot be explained rationally. They are categorised as "chukim", comprising such laws as the Red Heifer (Numeri 19). There two points of view regarding these laws; one believes that these laws do have a reason but that the ultimate explanation for mitzvot is beyond the human intellect, while the other believes that these laws have no meaning other than to instill obedience.

"Some Jewish scholars have held that these dietary laws should simply be categorized with a group of laws that are considered irrational in that there is no particular explanation for their existence. The reason for this is that there are some of God's regulations for mankind that the human mind is not necessarily capable of understanding. Related to this is the idea that the dietary laws were given as a demonstration of God's authority and that man should obey without asking for a reason" (William H. Shea, Clean and Unclean Meats, Biblical Research Institute, December 1988).

This view, however, has been rejected by most classical and modern Jewish authorities, and by modern biblical scholars. For example, Maimonides holds that all the laws given by God have a reason, that we are permitted to seek out what these reasons may be, and that we should feel comfortable in knowing that rational reasons exist for all of God's laws in the Torah, even if we are not sure of what some of these reasons are. For Maimonides, the idea that God gave laws without any reason is anathema.

Ritual purity and holiness

According to the Biblical book of Leviticus, the purpose of the laws is related to ritual purity and holiness. Indeed, the Hebrew word for "holiness" is etymologically related to the Hebrew word for "distinction" or "separation." This idea is generally accepted by most Jews today, and by many modern biblical scholars. Cultural anthropologist Mary Douglas has written an important work on just how the Israelites may have used the idea of distinction as a way to create holiness. Her seminal work, Purity and Danger (1966), is still studied today. One theory widely accepted today is that the laws serve as a distinction between the Israelites and the non-Israelite nations of the world. Gordon Wenham writes:

"The laws reminded Israel what sort of behaviour was expected of her, that she had been chosen to be holy in an unclean world."

Similarly, the practice of Kashrut serves as a daily exercise in self-discipline and self-control, strengthening the practitioner's ability to choose other difficult paths. The ability to rationally curb one's most basic appetites can be seen as the prerequisite to living in a civilized society. Also, the aspects of Kosher slaughter which emphasize and incorporate the need to avoid unnecessary suffering of the animal remind the believer that having the power of life and death or to cause suffering, even to a farm animal born and bred to be eaten, is a serious responsibility rather than a pleasure to be sought after; and that to actually indulge in pleasure in the power to cause suffering, even in so common a practice as hunting, is to damage our own moral sensibilities. Modern psychology confirms that those who have no empathy for the suffering or death of animals are greatly at risk for also having no regard for suffering and death of their fellow humans.

The prohibition against eating the fruits of a tree for the first three years also represents a capacity for self-discipline and self-denial, as well as a lengthy period of appreciation for the bounty of God, prior to losing oneself in its enjoyment. Similarly, the requirement to tithe one's harvest, aside from the social justice aspect, serves as a reminder that this material wealth is not purely the result of one's own efforts, but represents a gift from God; and as such, to share the gift with one's fellows does not represent a real loss to oneself.

Symbolic purpose

During the first few centuries of the common era some philosophers held that the laws of kashrut were symbolic in character. In this view, kosher animals represent virtues, while non-kosher animals represent vices. The first indication of this view can be found in the 1st century BCE Letter of Aristeas (par. 145-148, 153). It later reappears in the writings of Philo of Alexandria, and in the writings of some of the early Church fathers.

This hypothesis has long since been rejected by most Jewish and Christian scholars. Modern biblical criticism also has found nothing to support this hypothesis, although the concept of the pig as a particularly 'unclean' animal persists among Jews.

Although the symbolic explanation for kashrut has been largely rejected, a number of authorities maintain that the laws are intended to promote ethical and moral behaviour. A recent authority who has reexamined the symbolic/ethical meaning of kashrut is Rabbi Samson Raphael Hirsch (Germany, 19th century).

To some degree, the prohibition on combining milk with meat represents a symbolic separation between death, represented by the flesh of a dead animal, and life, represented by the milk required to sustain a newborn creature. The often-quoted humane component to this law is also of symbolic value; the Torah prohibits us from 'seething the kid in its mother's milk', a practice cruel only in concept, which would not be understood as cruelty by either the kid or its mother and would not cause them additional suffering; but which could still potentially inflame a human's taste for ultimate power over those creatures who are weaker. Thus, Kashrut prohibits the practice itself, even if the resulting mixture is to be discarded.

Similarly, the prohibition against consuming carnivorous mammals and birds, 'loathsome crawling creatures', and scavengers, as well as the prohibition against consuming sick or diseased animals, would seem to rely, at least in part, on their perceived symbolic character.

Maintenance of a separate culture

Related to the concept of kashrut being one aspect of Judaism as a separate people is the practical outcome of maintaining a specific national diet, similar to the concept of reproductive isolation in speciation. Just as two species who can interbreed will merge into one, the theory of cultural evolution requires a degree of social separation for two cultures to remain distinct entities. The laws of Kashrut had the effect of preventing socialization and intermarriage with non-Jews, helping the Jewish community maintain its identity. Wenham writes that

"circumcision was a private matter, but the food laws made one's Jewish faith a public affair. Observance of the food laws was one of the outward marks of a practising Jew, and this in turn enhanced Jewish attachment to them as a reminder of their special status" (Gordon J. Wenham, "The Theology of Unclean Food," The Evangelical Quarterly 53, January March 1981, p.6-15).

Hygiene

The laws of kashrut were once thought to have been based on hygiene. It was believed by some that kosher animals were healthier 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 phenomena that appear to be related to health. For instance glatt, the requirement that lungs be checked to be free of adhesions, would prevent consumption of animals who had been infected with tuberculosis; similarly, the ban on slaughtering of an unconscious animal would eliminate many sick and possibly infectious animals from being consumed. Such a rationale seems reasonable when considering the laws prohibiting the consumption of carrion birds or birds of prey (which are advantageous scavengers), as they may carry disease from the carrion they consume; shellfish, which as filter feeders can accumulate harmful parasites or toxins; or pork, which can harbor trichinosis if not properly cooked. Thus, it was natural for many to assume that all the laws of kashrut were merely hygienic in intent and origin. One of the rabbinical authorities that mention the hygiene hypothesis is Maimonides (in his "Guide for the Perplexed").

For a number of reasons, however, this idea has fallen out of favor among biblical scholars. The laws permit consumption of animals such as cows and sheep which can also harbor trichinosis, but not the consumption of horsemeat, which does not; fruits and vegetables may be eaten without prohibition even though there are many poisonous herbs, seeds, berries and fruits. Additionally, this hypothesis does not explain other parts of the Jewish dietary laws; for instance forbidding the consumption of fish without true scales, such as sharks, fruit from trees which are less than four years old, or residual blood in meat.

This is not to say that there could be no connection between the priestly laws of kashrut and hygiene. As in the dietary codes of many societies, it only makes sense that, over time, hygiene would likely play some role in the development of the dietary laws of Leviticus. The process of cultural evolution would eventually favor such a society over one that persisted in consumption of unhealthy foods.

Other reasons

There is also the suggestion of a practical aspect to some of the laws of Kashrut; for instance, the pig would not be a wise choice of domestic animal for a nation which was, at the time, a nomadic desert tribe.

The laws of Kashrut also conform to a general rule that human societies tend to separate food animals from companion animals, whether pets or working animals. For instance, where dogs are kept as pets, they are not eaten; in most countries, where horses are used as draft animals they are not eaten, but in countries where oxen and cows are used as draft animals, such as India, they are not eaten.

Like the laws for the slaughter of animals, laws against shellfish could actually be for the good of the creature. There is no painless method for the preparation of "bottom feeding" lobster and crab.

In probability, there are multiple reasons for the laws of Kashrut, with each law serving one or more than one purpose.

How kashrut is viewed by Judaism today

Orthodox Judaism and Conservative Judaism hold that Jews should follow the laws of kashrut. Reform Judaism and Reconstructionist Judaism hold that these laws are no longer binding. Most Jews in Reform Judaism have considered these laws a hindrance, rather than a facilitator, of piety; this is still the mainstream Reform position. Some parts of the Reform community have begun to move towards a more traditional position. This tradition-leaning faction agrees with mainstream Reform that the rules concerning kashrut are no longer binding, but holds that keeping kosher is an important way for people to bring holiness into their lives. Thus Jews are encouraged to consider adopting some or all of the rules of kashrut on a voluntary basis. The Reconstructionist movement advocates that its members accept some of the rules of kashrut, but does so in a non-binding fashion; their stance on kashrut is the same as the tradition-leaning wing of Reform. The different movements' positions on kashrut are reflective of their broader perspectives on Jewish law as a whole.

Many Jews who do not meet the complete requirements of Kashrut nevertheless maintain some subset of the laws; for instance, abstaining from pork or shellfish. The practice of maintaing the laws of Kashrut in the home but consuming nonKosher food in restaurants or elsewhere outside the home is so frequent that it has become a humorous cliche.

In English, the term kosher is frequently used in a metaphorical sense to mean "acceptable" or "approved", which is its conventional meaning in Hebrew. It is also part of some common product names. For example, "kosher salt" is a form of salt which has irregularly-shaped crystals, making it particularly suitable for preparing meat in accordance with Kashrut law because the increased surface area of the crystals absorbs blood more efficiently. Likewise, a "kosher pickle" is a particular style of pickle that originated in kosher delis, which themselves today represent a particular style of food, rather than adherence to the laws of Kashrut.

External links

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Resources on keeping kosher
- Guide to keeping kosher
- Reliable Kosher Symbols

On ritual slaughter

Pesach
- Rabbinical Assembly Passover guide

Miscellaneous
- The Torah and vegetarianism