After last shiur's philosophic introduction, we will now begin to review the actual laws of kashrut. The course will try to cover all elements, and will therefore begin from the basics. For those to whom most of this material will be familiar, this may serve as a review, though with the added benefit of seeing the relationship between the halakhic sources and the halakhic conclusions, since one of the principles of this course is to trace the halakhot to their sources.
We begin with the definitions of the kosher species. Some species are kosher and some are not. What are the guiding principles of the distinctions?
The Torah distinguishes between kosher and non-kosher land-animals, fowl, fish, and "creeping things," with different definitions for each category.
The Torah gives two defining characteristics of kosher land-animals (Vayikra 11,2-3). [If you can, you should look up these verses in the Hebrew]:
Speak to the Israelites, saying: This is the living thing that you shall eat, from all the animals on the land.
All that have split hooves, whose hooves are cleft, and chew their cud, from the animals, you may eat it.
For an animal to be kosher, it must have BOTH of these characteristics - have split hooves and chew its cud. The Torah proceeds to list several animals who have only one of the two, and are therefore not kosher - camels, rabbits and badgers, which chew their cud but do not have split hooves, and the pig, which has the opposite features. (Verses 4-7). In Devarim 14,5, the Torah lists ten kosher animals, not all of which are readily identifiable in modern terminology. The domesticated animals in the list include cattle and sheep (and goats), and in the wild animal category appear the deer and the antelope.
Halakhically, the determining factor is the presence of the two characteristics. The Rambam states that there are in fact no other kosher animals other than the ten species listed in Devarim, but since not all are identified, and the halakhic definition of what constitutes a distinct species is also not clear, this is not particularly helpful. In the end, were there to be a question concerning a new species, many authorities agree that the presence of the two characteristics would be sufficient to declare that species kosher. The Chazon Ish (YD 11,4) however, ruled that practically speaking we can only eat those species that historically have been eaten by the Jewish communities as kosher. This restriction has the status of custom (minhag).
The signs of a kosher animal apply to the species and not to the individual animal. Hence if a cow should happen not to have split hooves it would still be kosher. The question that arises, of course, is how the Torah defines a species. The answer in halakha is that "haba min hatamei tamei, ve-haba min hatahor tahor." If a kosher animal gives birth, the offspring is kosher even if it lacks the signs of a kosher animal and the reverse is true as well. The context of this statement in the Talmud is the possibility of a mutation. Modern techniques of reproductive engineering might give rise to interesting possibilities of having one species gestate and give birth to a different genetic species. The status of the offspring in such a case will undoubtedly require extensive halakhic analysis.
It has been noted that all carnivorous animals are not kosher. The opposite is not true - there are non-kosher animals that are not carnivorous. While this is not a halakhic definition, it does have philosophic significance, especially according to those thinkers who explained the forbidden species as embodying bad or harmful traits. Animals that kill to eat, are not fit to be consumed by humans.
These you may eat, from all that is in the water; all that have fins and scales, in the water, in the seas and the streams, them may you eat.
But any that do not have fins and scales, in the seas and streams, from all that swarm in the water, and from all living souls in the water, sheketz are they to you (Vayikra 11,9-10).
In fact, the Talmud declares that, in actual fact, all fish that have scales ("kaskeset) have fins ("snapir"), and therefore, practically speaking, it is sufficient to establish the presence of scales to declare a fish kosher.
As is clear from the verse, this definition applies to all "that is in the water." The modern scientific definition of fish, as opposed to sea mammals and other creatures, is therefore not relevant. Hence, all sea creatures that are not classified scientifically as fish, such as crustaceans or mammals, are not kosher, since they do not possess scales. This accounts for the most common cases of non-kosher seafood - all shellfish (clams, lobsters, oysters) and whales, for instance.
There are also genuine fish that do not have scales, for instance, eels. Halakhically, all forms of scales are sufficient, whether they are found on the fish at all stages of life or only at some, providing they are removable from the skin (even if it requires a knife). There are some fish that have a form of bone-protuberances which cannot be removed without damaging the skin (such as sharks), and this is not considered to be true scales halakhically.
[Note: True caviar is made from the eggs of sturgeon. Some two hundred years ago, a controversy arose concerning the kashrut of sturgeon. This fish does not have regular scales, but a series of five hard skin-coverings that cannot be removed from the skin without damaging it. However, it seems that by boiling the fish or treating it in some other way, it is possible to remove these scales (the scientific classification is placoid scales). The question is whether this could be considered halakhic scales, which have to be external and ancillary to the actual body of the fish. (The halakhic formulation is that the scales be like a garment covering the fish and not part of his body.) There was also some question whether in fact the skin remains intact, since the processing tends to affect it as well. The preponderance of rabbinic opinion is that sturgeon is not a kosher fish, and therefore genuine (black) caviar is not kosher.]
For those with a scientific education, ctenoid and cycloid scales are kosher; ganoid (shark scales) and placoid (sturgeon) scales are not.
In buying non-fresh fish, there are often many other considerations in regard to the preparation of the fish, which we shall get to in the course of the lectures. At this point, we are only considering the kashrut of the species. On the other hand, a kosher fish is completely kosher, without any parts that must be discarded, unlike animals and birds, which have parts (blood, fat) which are not permitted even when the species are kosher. But that too will have to wait our discussion of each topic.
[Because there are thousands of fish species, and the names of fish tend to be varied and often of quite local character, it is notoriously difficult to compose an exhaustive list of kosher fish. One of the best lists available, published by the OU about eight years ago, can be seen on the web at
The Torah does not give any "simanim," identifying characteristics of kosher birds. Instead, the Torah states that you may eat all kosher birds, followed by a list of the birds that you are not permitted to eat. (Vayikra 11,13-19 and Devarim 14,12-18. Since an exact translation of the twenty-four forbidden species is impossible, I am not bothering to quote the [English] verses, but you should look it up. The list includes the hawk, the raven, the owl, the vulture, and the bat.) The halakhic conclusion of these verses is that all birds are kosher except for the ones listed in the prohibited list. The only problem is defining the exact identification of the birds listed, and drawing a correspondence with known species. This problem is not only one of translation. Since we do not have a definition of the halakhic nature of "species," even if we knew what a given term in the Torah meant, we would still have some doubt concerning the range of birds included in a given category.
The Talmud (Chullin 61a) does give a list of characteristics by which to recognize kosher and non-kosher birds. The basis of this list is a rabbinic tradition.
1. The first rule is that any bird of prey is not kosher.
If it is not a bird of prey, then it is kosher if it has three positive signs:
1. An extra talon opposite the others.
2. A craw.
3. Its stomach lining can be peeled.
The most problematic requirement is that it not be a bird of prey, which may not be obvious from looking at it. While the Talmud gives some rules for identifying birds of prey, these are not conclusive. The Talmud (Chullin 83b) states: "R. Yitzchak said: A kosher bird is eaten on the basis of a tradition."
The meaning of this statement in context is permissive - it states that one does not need to personally know that the bird is not a bird of prey if there is a positive tradition that it is eaten. But because identification is so difficult, the statement has been widened by basically reading it in the negative - no bird can be eaten UNLESS there exists a positive living tradition attesting to its kashrut. In the language of the Rama: "There is an opinion that... no bird should be eaten unless there exists a tradition that it is kosher, and this is the accepted practice and it should not be changed" (Yoreh Deah 82,3).
Hence, practically speaking, both the Torah's list and the defining characteristics found in the Talmud are not relevant any more. A kosher bird is one that has been traditionally eaten by Jewish communities.
The birds that are included in this category are chickens, domestic ducks and geese, pigeons and doves, and quail. There existed in the past local traditions to eat other birds, for instance, pheasant. There is some halakhic doubt whether this would suffice to permit it generally today. (See Igrot Moshe YD,34 who prohibits pheasant.)
The interesting question arises when a "new" bird appears. The classic case of a new bird is the turkey, which is native to America. There were originally poskim who felt that it was not kosher, since obviously there did not exist a positive tradition that it could be eaten. Nonetheless, today it is accepted as kosher in all Jewish communities. As far as we are concerned today, there exists a tradition to eat it. The original genesis of this tradition was based first on the similarity to a chicken, as well as the fact that it met the requirements of not being a bird of prey and having all three characteristics listed in the Talmud.
[The ruling of the Chazon Ish cited above, that one should not eat the meat of an animal without a positive tradition concerning its kashrut, even if it has the two characteristics of kosher animals, is basically an extension of the rule of kosher birds.]
The fourth type of living thing to which laws of species applies is called "sheretz" in the Torah, a creature that creeps. This includes reptiles, insects (including flying insects and water insects), and such creatures as the mole and the mouse. Basically, they are all not kosher. The most important ramification of this halakha, other than for one who happens to want to eat roast rattlesnake or the like, is a need to carefully inspect fruits and vegetables for bugs and worms that might be present, even if they are very small. We will return to this topic in a later shiur.
There is one type of permitted "creeping" creature - grasshoppers which have four legs, four wings which cover its entire body. Practically speaking, this permissibility of some types of locust is cancelled, due to an inability to fully identify the permitted species. There were localities in Morocco and in Yemen where a living tradition of permitted locusts existed. (Apparently, they are quite tasty, though naturally that is a somewhat personal conclusion.)
E. Animal Products
Remember the rule defining species - haba min hatamei tamei, ve-haba min hatahor tahor? Whatever comes out of a non-kosher animal is not kosher, and vice-versa. This rule of origin applies to eggs as well, so that the eggs of kosher birds are kosher, but the eggs of non-kosher birds are not. If you cannot eat the hen, you cannot eat the egg. The same thing is true of milk and milk products - cow milk is kosher, but horse milk is not.
The permissibility to eat eggs and milk products is not as obvious as it might seem on first glance. One of the prohibitions of the Torah, in fact, one of the seven laws which apply, according to Torah law, even to non-Jews, is "ever min ha-chai." It is forbidden to eat any part of an animal before the animal has died. (Of course, Jewish law requires that it be slaughtered in a particular manner as well.) Off hand, this should have prohibited milk and eggs of a living creature. The Talmud had to find an explicit source to prove that the Torah specifically permitted milk of kosher animals (Bekhorot 6b).
This same principle will also lead to the conclusion that milk is prohibited if it comes from a kosher-species animal that is forbidden for another reason; for instance, if it is a treifa (an animal bearing a life-threatening defect).
Is human meat permitted? This rather ghastly question is answered by the Rambam (Maakhalot Assurot 2,3) in the negative. Although the negative prohibition to eat a mammal not possessing the two characteristics is not intended to include human meat, the Rambam states that there is a positive commandment which states that you may eat only these species - and then lists ten kosher species. The Rambam claims that this infers a prohibition on humans, who are not one of the ten permitted animals. Because humans are not included in the negative prohibition, the Rambam states that the rule that haba min hatamei tamei does not apply, and hence human milk and blood is permitted. For this reason, it is permitted to swallow the blood bleeding in one's mouth or to suck on a wound. There is a rabbinic prohibition to consume human blood once it has left the body, for the simple reason that it looks like animal blood.
Next shiur we will discuss those parts of (kosher) animals which are not kosher, especially the prohibition of blood.