On the contrary, It is written (Deut. 18:14): "But thou art otherwise instructed by the Lord thy God": from which words we may gather that these observances were instituted by God to be a special prerogative of that people. Therefore they are not without reason or cause.
I answer that, The Jewish people, as stated above (A. 5), were specially chosen for the worship of God, and among them the priests themselves were specially set apart for that purpose. And just as other things that are applied to the divine worship, need to be marked in some particular way so that they be worthy of the worship of God; so too in that people's, and especially the priests', mode of life, there needed to be certain special things befitting the divine worship, whether spiritual or corporal. Now the worship prescribed by the Law foreshadowed the mystery of Christ: so that whatever they did was a figure of things pertaining to Christ, according to 1 Cor. 10:11: "All these things happened to them in figures." Consequently the reasons for these observances may be taken in two ways, first according to their fittingness to the worship of God; secondly, according as they foreshadow something touching the Christian mode of life.
Reply Obj. 1: As stated above (A. 5, ad 4, 5), the Law distinguished a twofold pollution or uncleanness; one, that of sin, whereby the soul was defiled; and another consisting in some kind of corruption, whereby the body was in some way infected. Speaking then of the first-mentioned uncleanness, no kind of food is unclean, or can defile a man, by reason of its nature; wherefore we read (Matt. 15:11): "Not that which goeth into the mouth defileth a man; but what cometh out of the mouth, this defileth a man": which words are explained (Matt. 15:17) as referring to sins. Yet certain foods can defile the soul accidentally; in so far as man partakes of them against obedience or a vow, or from excessive concupiscence; or through their being an incentive to lust, for which reason some refrain from wine and flesh-meat.
If, however, we speak of bodily uncleanness, consisting in some kind of corruption, the flesh of certain animals is unclean, either because like the pig they feed on unclean things; or because their life is among unclean surroundings: thus certain animals, like moles and mice and such like, live underground, whence they contract a certain unpleasant smell; or because their flesh, through being too moist or too dry, engenders corrupt humors in the human body. Hence they were forbidden to eat the flesh of flat-footed animals, i.e. animals having an uncloven hoof, on account of their earthiness; and in like manner they were forbidden to eat the flesh of animals that have many clefts in their feet, because such are very fierce and their flesh is very dry, such as the flesh of lions and the like. For the same reason they were forbidden to eat certain birds of prey the flesh of which is very dry, and certain water-fowl on account of their exceeding humidity. In like manner certain fish lacking fins and scales were prohibited on account of their excessive moisture; such as eels and the like. They were, however, allowed to eat ruminants and animals with a divided hoof, because in such animals the humors are well absorbed, and their nature well balanced: for neither are they too moist, as is indicated by the hoof; nor are they too earthy, which is shown by their having not a flat but a cloven hoof. Of fishes they were allowed to partake of the drier kinds, of which the fins and scales are an indication, because thereby the moist nature of the fish is tempered. Of birds they were allowed to eat the tamer kinds, such as hens, partridges, and the like. Another reason was detestation of idolatry: because the Gentiles, and especially the Egyptians, among whom they had grown up, offered up these forbidden animals to their idols, or employed them for the purpose of sorcery: whereas they did not eat those animals which the Jews were allowed to eat, but worshipped them as gods, or abstained, for some other motive, from eating them, as stated above (A. 3, ad 2). The third reason was to prevent excessive care about food: wherefore they were allowed to eat those animals which could be procured easily and promptly.
With regard to blood and fat, they were forbidden to partake of those of any animals whatever without exception. Blood was forbidden, both in order to avoid cruelty, that they might abhor the shedding of human blood, as stated above (A. 3, ad 8); and in order to shun idolatrous rites whereby it was customary for men to collect the blood and to gather together around it for a banquet in honor of the idols, to whom they held the blood to be most acceptable. Hence the Lord commanded the blood to be poured out and to be covered with earth (Lev. 17:13). For the same reason they were forbidden to eat animals that had been suffocated or strangled: because the blood of these animals would not be separated from the body: or because this form of death is very painful to the victim; and the Lord wished to withdraw them from cruelty even in regard to irrational animals, so as to be less inclined to be cruel to other men, through being used to be kind to beasts. They were forbidden to eat the fat: both because idolaters ate it in honor of their gods; and because it used to be burnt in honor of God; and, again, because blood and fat are not nutritious, which is the cause assigned by Rabbi Moses (Doct. Perplex. iii). The reason why they were forbidden to eat the sinews is given in Gen. 32:32, where it is stated that "the children of Israel . . . eat not the sinew . . . because he touched the sinew of" Jacob's "thigh and it shrank."
The figurative reason for these things is that all these animals signified certain sins, in token of which those animals were prohibited. Hence Augustine says (Contra Faustum iv, 7): "If the swine and lamb be called in question, both are clean by nature, because all God's creatures are good: yet the lamb is clean, and the pig is unclean in a certain signification. Thus if you speak of a foolish, and of a wise man, each of these expressions is clean considered in the nature of the sound, letters and syllables of which it is composed: but in signification, the one is clean, the other unclean." The animal that chews the cud and has a divided hoof, is clean in signification. Because division of the hoof is a figure of the two Testaments: or of the Father and Son: or of the two natures in Christ: of the distinction of good and evil. While chewing the cud signifies meditation on the Scriptures and a sound understanding thereof; and whoever lacks either of these is spiritually unclean. In like manner those fish that have scales and fins are clean in signification. Because fins signify the heavenly or contemplative life; while scales signify a life of trials, each of which is required for spiritual cleanness. Of birds certain kinds were forbidden. In the eagle which flies at a great height, pride is forbidden: in the griffon which is hostile to horses and men, cruelty of powerful men is prohibited. The osprey, which feeds on very small birds, signifies those who oppress the poor. The kite, which is full of cunning, denotes those who are fraudulent in their dealings. The vulture, which follows an army, expecting to feed on the carcases of the slain, signifies those who like others to die or to fight among themselves that they may gain thereby. Birds of the raven kind signify those who are blackened by their lusts; or those who lack kindly feelings, for the raven did not return when once it had been let loose from the ark. The ostrich which, though a bird, cannot fly, and is always on the ground, signifies those who fight for God's cause, and at the same time are taken up with worldly business. The owl, which sees clearly at night, but cannot see in the daytime, denotes those who are clever in temporal affairs, but dull in spiritual matters. The gull, which both flies in the air and swims in the water, signifies those who are partial both to Circumcision and to Baptism: or else it denotes those who would fly by contemplation, yet dwell in the waters of sensual delights. The hawk, which helps men to seize the prey, is a figure of those who assist the strong to prey on the poor. The screech-owl, which seeks its food by night but hides by day, signifies the lustful man who seeks to lie hidden in his deeds of darkness. The cormorant, so constituted that it can stay a long time under water, denotes the glutton who plunges into the waters of pleasure. The ibis is an African bird with a long beak, and feeds on snakes; and perhaps it is the same as the stork: it signifies the envious man, who refreshes himself with the ills of others, as with snakes. The swan is bright in color, and by the aid of its long neck extracts its food from deep places on land or water: it may denote those who seek earthly profit though an external brightness of virtue. The bittern is a bird of the East: it has a long beak, and its jaws are furnished with follicules, wherein it stores its food at first, after a time proceeding to digest it: it is a figure of the miser, who is excessively careful in hoarding up the necessaries of life. The coot [*Douay: porphyrion. St. Thomas' description tallies with the coot or moorhen: though of course he is mistaken about the feet differing from one another.] has this peculiarity apart from other birds, that it has a webbed foot for swimming, and a cloven foot for walking: for it swims like a duck in the water, and walks like a partridge on land: it drinks only when it bites, since it dips all its food in water: it is a figure of a man who will not take advice, and does nothing but what is soaked in the water of his own will. The heron [*Vulg.: herodionem], commonly called a falcon, signifies those whose "feet are swift to shed blood" (Ps. 13:3). The plover [*Here, again, the Douay translators transcribed from the Vulgate: charadrion; charadrius is the generic name for all plovers.], which is a garrulous bird, signifies the gossip. The hoopoe, which builds its nest on dung, feeds on foetid ordure, and whose song is like a groan, denotes worldly grief which works death in those who are unclean. The bat, which flies near the ground, signifies those who being gifted with worldly knowledge, seek none but earthly things. Of fowls and quadrupeds those alone were permitted which have the hind-legs longer than the forelegs, so that they can leap: whereas those were forbidden which cling rather to the earth: because those who abuse the doctrine of the four Evangelists, so that they are not lifted up thereby, are reputed unclean. By the prohibition of blood, fat and nerves, we are to understand the forbidding of cruelty, lust, and bravery in committing sin.
Reply Obj. 2: Men were wont to eat plants and other products of the soil even before the deluge: but the eating of flesh seems to have been introduced after the deluge; for it is written (Gen. 9:3): "Even as the green herbs have I delivered . . . all" flesh "to you." The reason for this was that the eating of the products of the soil savors rather of a simple life; whereas the eating of flesh savors of delicate and over-careful living. For the soil gives birth to the herb of its own accord; and such like products of the earth may be had in great quantities with very little effort: whereas no small trouble is necessary either to rear or to catch an animal. Consequently God being wishful to bring His people back to a more simple way of living, forbade them to eat many kinds of animals, but not those things that are produced by the soil. Another reason may be that animals were offered to idols, while the products of the soil were not.
The Reply to the Third Objection is clear from what has been said (ad 1).
Reply Obj. 4: Although the kid that is slain has no perception of the manner in which its flesh is cooked, yet it would seem to savor of heartlessness if the dam's milk, which was intended for the nourishment of her offspring, were served up on the same dish. It might also be said that the Gentiles in celebrating the feasts of their idols prepared the flesh of kids in this manner, for the purpose of sacrifice or banquet: hence (Ex. 23) after the solemnities to be celebrated under the Law had been foretold, it is added: "Thou shalt not boil a kid in the milk of its dam." The figurative reason for this prohibition is this: the kid, signifying Christ, on account of "the likeness of sinful flesh" (Rom. 8:3), was not to be seethed, i.e. slain, by the Jews, "in the milk of its dam," i.e. during His infancy. Or else it signifies that the kid, i.e. the sinner, should not be boiled in the milk of its dam, i.e. should not be cajoled by flattery.
Reply Obj. 5: The Gentiles offered their gods the first-fruits, which they held to bring them good luck: or they burnt them for the purpose of secrecy. Consequently (the Israelites) were commanded to look upon the fruits of the first three years as unclean: for in that country nearly all the trees bear fruit in three years' time; those trees, to wit, that are cultivated either from seed, or from a graft, or from a cutting: but it seldom happens that the fruit-stones or seeds encased in a pod are sown: since it would take a longer time for these to bear fruit: and the Law considered what happened most frequently. The fruits, however, of the fourth year, as being the firstlings of clean fruits, were offered to God: and from the fifth year onward they were eaten.