From, Meir Soloveitchik, https://tikvahfund.org/uncategorized/locusts-giraffes-and-the-meaning-of-kashrut/
A second theory of kashrut is of the sort propounded by the nineteenth-century German rabbinic leader Samson Raphael Hirsch, who attempted to refashion the medical approach into a philosophical form. Hirsch argues that while man is both body and soul, “the body of man should be the servant of his spirit.” This, he continues, can be accomplished only if the body“ is not too active in a carnal direction, if it is passive and indifferent to its own desires, and if it is submissive to the demands of the soul.” Furthermore, the physical structure of man is influenced by “the kind of food he consumes,” and therefore vegetables are the most preferable food, as they are the most passive substance; thus we find that “all vegetables are permitted for food, without discrimination.” Next in order of desirability are those animals that are herbivorous and therefore nearer to the vegetable world. The Tora therefore permits animals that are herbivores and ruminants, and “spend a great deal of time in the absorption of food, which may be termed the vegetative activity of animals.” Similarly, Hirsch continues, the Tora forbade all fowl that are not passive in nature, such as birds of prey, as well as “lively artistic birds” such as songbirds or those that indicate artistry in building a nest. Finally, creepers and fliers are forbidden because ingestion of insects is dulling to the intellect.
Leon Kass, The Hungry Soul
“The principles important to Genesis 1—place, form or kind, motion and life—are all at work in Leviticus 11.”
“Ruled out are:
1. Creatures that have no proper or unambiguous place; for example the amphibians.
2. Creatures that have no proper form. Either indefinite form (jellyfish), deceptive form (eel) or incomplete form (incompletely cloven-hoofed animals.
3. Creatures that violate proper locomotion, such as those animals that live in water but walk on land (lobsters); that that live on land but swarm as in water.
4. Creatures that violate the original dietary code, showing no respect for life—that is the carnivorous ones.
“Cud chewers are so far from eating other animals that they finally chew and swallow only the homogenized stuff they have already once swallowed and raised: When the pig, a notorious omnivore, is declared unclean, the Torah says it is because ‘he does not chew the chew’ presenting by implication, as it were, the ideal of the perfect fit of activity and object…One should chew not life but chew—that is, that which is fit for chewing. The chew-chewers are poles apart from that first accursed and most unclean animal, the belly-crawling serpent, which is in fact a moving digestive tract and which ‘voraciously’ swallows its prey whole and live.”
“The dietary laws should remind us not only of the created order but of the order as created, not only of the intelligible separations and forms but of the mysterious source of form, separation and intelligibility.”
“And how might one become holier through observing these separations? Two suggestions. On the one hand, through obedience. One reduces the distance between the holy and the profane by sanctifying the latter through obedience to the former. The low is made high—or at least higher—through acknowledgement of its dependence on the high; the high is “brought down,” “democratized,” and given concrete expression in the forms that govern ordinary life….
On the other hand, through imitation: God seems to say to the creature made in His image, “You should make distinctions because I make distinctions.”
9 About noon the following day as they were on their journey and approaching the city, Peter went up on the roof to pray. 10 He became hungry and wanted something to eat, and while the meal was being prepared, he fell into a trance. 11 He saw heaven opened and something like a large sheet being let down to earth by its four corners. 12 It contained all kinds of four-footed animals, as well as reptiles and birds. 13 Then a voice told him, “Get up, Peter. Kill and eat.”
14 “Surely not, Lord!” Peter replied. “I have never eaten anything impure or unclean.”
15 The voice spoke to him a second time, “Do not call anything impure that God has made clean.”
16 This happened three times, and immediately the sheet was taken back to heaven.
34 Then Peter began to speak: “I now realize how true it is that God does not show favoritism 35 but accepts from every nation the one who fears him and does what is right.
From Meir Soloveitchik, https://tikvahfund.org/uncategorized/locusts-giraffes-and-the-meaning-of-kashrut/
It is crucial to stress that, despite the emphasis on one’s ancestry, the definition of Jewish distinctiveness is not a racial one. It is not a question of one’s genetic makeup at birth—for indeed, this is explicitly dismissed in the case of the animal that is born with traits that would seem to render it non-kosher. What is suggested, rather, is that there is something other than genetic reality that is transmitted from one’s parents: A kind of familial identity that makes us part of a specific collective, a nation, passed from one generation to the next. Membership in the chosen people is indeed something that one inherits and cannot repudiate regardless of his beliefs or actions: It is a covenantal obligation that is binding on the Jew from one generation to the next, and which inevitably links each Jew to future generations. At the same time, however, it is a covenantal identity that is open for others to join: A non-Jew may convert to Judaism, entering into the covenant of this nation, and binding himself not merely to the same set of obligations, but to that essential, chosen community, an identity which he then passes on to his children. Jewish identity is thus inherently open to all, regardless of their biology. Yet it is also, indeed primarily, transmitted from parents to children—not as genetics, but as membership in a familial and national community.