For millennia, Jews have kept these laws for the most basic reason of all: Because the Torah tells us to do so. But we also need to start explaining the underlying philosophy behind kashrus, to show that there is both internal consistency and a higher purpose in being careful about the foods that we eat. What does kashrus have to do with holiness?
The Torah tells us which animals can be eaten, and which cannot – among mammals, we can eat animals that have split hooves and chew the cud; and, among others, we can also eat grasshoppers. Grasshoppers?! Where does that come from?
Like the rest of the Torah, the answer is not far from us; the explanation for kosher animals can be found within the words of the Torah itself!
Firstly, we are commanded to be a holy people. As such, we are meant to be always seeking to connect the earth to the sky – unify the waters above and below. So holiness, as the coexistence of earth and spirit, requires the elevation of the products of the earth.
Indeed, the Gemara says that for an animal to be kosher, it must be able to rise up from the ground. Kosher mammals must have split hooves – their connection to the earth is incomplete, incapable of properly bonding between the earth and the animal. It also partially explains grasshoppers, which are described in the Torah as having “legs above their feet, to leap with upon the earth.” Grasshoppers share that aspect with cows and sheep: they also can be described as partially connected to heaven, just by virtue of not being fully connected to the earth. So this explains the Torah’s commandment to notice the feet and legs of animals – for us to be holy, we can only eat animals whose bodies are not solidly in contact with the earth.
But the Torah does not just tell us to eat animals that have cloven hoofs. The second part of that commandment is that we must be sensitive to whether the animal chews its cud; in other words, the only mammals we can eat are ruminants.
Animals that chew their cuds are the only animals that can fully digest plants. By contrast, monogastric animals can only incompletely digest grain and vegetables. Key plant components that cannot be digested by unkosher animals such as dogs, minks, and pigs (among many others) include the plant compounds stachyose and raffinose. And so the Torah tells us that the animals that we, as a holy nation, can eat must be animals that fully digest plants. Grasshoppers, by the way, are also preferentially grain and cereal consumers, and they also digest plants in full.
Animals that cannot digest plants in full are, in a sense, incomplete. Raffinose and Stachyose are both sugars, so literally, the animals we can eat must be able to benefit from the sweetness of the land!
But this just leads us to another question: are we really saying that an animal Hashem created is somehow incomplete? We don’t have to: the Torah does it for us.
And to every beast of the earth, and to every bird of the air, and to every thing that creeps upon the earth, where there is life, I have given every green herb for food.372
Animals that eat green herbs for food are complete in themselves: they completely fulfill the function of an animal by fully digesting plants.
So when Hashem made the cow, it was a complete act, because the cow could fulfill the Torah’s injunction for animals to live off of plants. But dogs are incomplete animals; because, while they are successful organisms, dogs cannot follow the Torah by subsisting on plant life. We can consume all animals that are made perfect according to the Torah, and which are already able to separate from the earth and make an aliyah. These animals allow us to fulfill our own mission in life.
So much for animals. What about fish?
The Torah tells us that we may only eat fish that have fins and scales.
We, as a holy nation, start grounded in the earth (or waters of the mikvah). And then we live our lives trying to elevate and combine those physical roots with the spiritual heights. As has already been explained, the land animals we eat must be fully products of the earth, but also must have started to grow away from it. They are the first step toward a higher plane.
Fish, of course, have different rules – but the same explanation! In order for a water creature to be kosher, it must have two things: fins and scales. And the Talmud explains that a fish with scales also has a distinct spinal column; in other words, it has bones.
Fish are already very well connected to the “waters below,” in that they can all exist in a kosher mikvah (ponds, lakes, and the ocean all qualify). The requirement for fins and scales is a requirement that the animals, like the land mammals with cloven hooves, are sufficiently distinct from their environment so as to rise above it.
Fins are a method of propulsion, already allowing the fish (unlike, say, a clam) to start the journey toward spirituality, to move itself upward. The finned fish (unlike, for example a jellyfish) can readily move against the current, to separate itself from its medium.
The fins themselves also act as a means of separation. A fish with fins does not have to use its entire body like an eel or squid does, in order to move through the water. The fins are an intermediary, causing a further division between the fish and the water.
Scales are another form of separation from the water. The scales of a kosher fish can be detached, by hand or with a knife, without ripping the skin, which means that the scales, like the split hooves of a cow, form another intermediary layer, separating the fish from its habitat.
Cartilage, which takes the place of bones in sharks, is essentially a hardened jelly-‐type substance, which is quite similar to water itself. Bones of a spinal column, on the other hand, are distinct from the water. The fish we can eat are the water creatures that are separate from the water, and can elevate themselves from within it.
It is often said that the secret to really great food is to start with the best ingredients. We could say the same thing about holiness: it is essential to start with the right ingredients. To be a holy people, striving to combine the physical and the spiritual, we must also limit our consumption to those animals that are also distinct from their environment and are able to reach upward.
The laws of Kashrus are entirely consistent with the rest of the Torah’s laws telling Jews how to be a holy nation. The answers are within reach.