What is the Reason for Kashrut?

Why are we allowed to eat some animals but prohibited from eating others?

Why are some mammals, birds, fish and insects kosher, while others, along with all reptiles and amphibians, are not kosher (or to use the colloquial if inaccurate term, “treif”)?

One of the exhibit halls at the Biblical Museum of Natural History is the Hall of Kosher Classification, which displays a range of both live and non-live kosher and treif creatures, along with many related materials. Many visitors have asked me about the reasons for these laws, and I’ve given it a lot of thought.

In rabbinic literature there were arguments about non-kosher species being unhealthy or metaphysically affecting one’s personality, but these are not scientifically sustainable. A number of academic Bible scholars, such as Mary Douglas and Leon Kass, have attempted to give systematic explanations, but these tend to strain credulity.

To my mind - and I think I recall seeing this written somewhere many years ago, but I don’t recall where - people are barking up the wrong tree. There is not one reason for why certain animals are kosher and others are treif. Instead, there are several reasons, which function at two different levels.

At the first level are the reasons for the concept of kashrut, rather than the specifics of which animals are kosher and treif. And at the second level are reasons for the choice of which animals are kosher and treif - and there can be several of these, rather than a single principle which governs everything.

With regard to the concept of kashrut, the Torah (Vayikra 11:45-47) says explicitly that it is about God’s People being required to practice kedusha, sanctity. Sanctity is about separating out things to be special. Shabbat is sanctified by being separated out from the rest of the week, with kiddush at the beginning and havdalah at the end. With kashrut, we separate themselves from certain foods, and thereby also separate our nation culturally from other nations, so that we survive with a distinct identity and remain focused on our mission.

Then we get to the second level, which is reasons for the choice of which animals we separate ourselves from. Here, there is not a single reason which explains each animal, but rather a number of different factors.

One of these is a general preference for avoiding creatures that are carnivorous. This is a theme that is undeniably seen with mammals and especially birds, with which most of the prohibited types are either birds of prey, carnivores (like the stork), or fishing birds (like the seagull, cormorant and heron). As to why we must not eat carnivorous creatures, it’s not entirely clear if it is symbolic, psychological, or something else.

And yet this alone does not suffice. The Torah does not tell us to simply avoid carnivores; and there are many herbivorous creatures that are forbidden, because they do not possess the attributes of split hooves and bringing up the cud. Many have attempted to give symbolic or mystical significance to these characteristics. I have not found any of these to be convincing, and I am wondering if perhaps an entirely different approach is required.

Perhaps these characteristics are not inherently significant, but rather are a way of bringing about a desired result, which is the inclusion of sheep and goats and cattle, but the exclusion of camels, hares, hyraxes and pigs (and horses). This in turn may be desirable in order to only permit animals that are herded. Alternately, perhaps the point is that the camel, hare, hyrax and pig were all prominently eaten by certain cultures, and would relate to kashrut’s primary theme of cultural distinction. In fact, some state that the reason why the Torah specified these animals by name, even though they are obviously already prohibited since they lack both kosher signs, was to hammer home the point that even though these animals are commonly eaten by others in the area, they are forbidden to the Jewish People.

Another theme is avoiding creatures that are disgusting, as discussed in the previous post. This is clearly the reason for the prohibition of most insects, which the Torah explicitly refers to with the word sheketz, repulsive. But it may also be the reason for the prohibition of the pig, along with birds such as the hoopoe - a gaudy but foul and poisonous bird that smears its young with noxious excretions (it bothers me intensely that the hoopoe won the popular vote to be Israel’s national bird), and perhaps also the bat.

Another possibility for the bat being prohibited is that it is an “aberrant” creature, being winged like a bird but otherwise resembling a land animal. The same problem of “aberrancy” may apply to the forbidden sea creatures, which diverge from the classic “fins and scales” form of fish.

There is more to still be discussed and discovered about all this. But I think that the general approach of a dual-layered set of reasons, with multiple factors at the second level, is the most robust.