St. Jerome left it in writing, in Epistle 125 which he sent to Damasus, that Tertullian had written an excellent disputation as to why God, who had made all things very good, commanded to be brought into the ark of Noah, together with the clean animals, the unclean ones also. That this question was indeed treated fully and completely by Tertullian one may estimate from this: that St. Jerome, when he was consulted on the same question by Damasus, was unwilling to touch its explanation — as though he judged that nothing of great moment could be added by himself to that disputation of Tertullian.¹

But since that book of Tertullian has by no means come down to us, we have not been able to become partakers either of his teaching or of his opinion. But to that very question one might briefly reply — as much, that is, as suffices for our purpose — thus: that no animal is by nature unclean, but that every animal is of the number of those which God made, each in its own kind, very good; and that certain ones are called unclean not in themselves nor according to nature, but either by the established opinions of men, or in relation to the food of man, or for the sake of some signification and the sake of some mystery. Now those animals which are named unclean had necessarily to be brought into the ark, lest so many species of them — which hold, without controversy, the chief place of dignity and nobility among the animals, such as the lion, the horse, and the elephant — should perish in the flood. But, leaving these matters aside, let us explain with diligence and care the things which God commanded Noah concerning the animals to be brought into the ark.²

God commanded Noah to bring into the ark two each of the unclean animals, but seven each of the clean. But this command of God has two questions, of which the first is this: How could the distinction of clean and unclean animals exist in observance and use before the Flood, since it was introduced by the law of Moses — the promulgation of which law the Flood preceded by eight hundred years? To this question a threefold answer is usually given. St. Chrysostom, in his twentie[th homily]…³

…answers, in the twenty-fourth homily on Genesis, that the distinction of clean and unclean animals was known to Noah either by the natural judgment and prudence of reason, or by some special revelation of God; and Didymus too is reported to have thought and handed down the same in the Catena. And the words of Chrysostom are these: “It would be worthwhile here to inquire whence that just man knew which animals were clean and which unclean: for this distinction had not yet been made, which Moses afterward established in his laws. Whence, then, did he know? Was it from himself, and from a doctrine implanted in his nature? Now nothing is unclean in itself among the things which God made: for how should we call any creature unclean, since every one was once approved by God, when Moses says: ‘God saw all the things that he had made, and they were very good’ (Gen. 1)?⁴

“But nature afterward distinguished these things of itself. And that this is true, consider how in some places certain men abstain from some things as unclean, while others eat those very things: so great is the force of custom among men in either direction. So also it was in the time of Noah. But that knowledge implanted in the man taught him which things were suitable for food and which unclean — not that they were such in themselves, but because they were held to be unclean. For what reason, tell me, pray, do we judge the ass unclean, and shun the eating of it, although it feeds on legumes, while other quadrupeds, though they feed on unclean things, we nevertheless think suitable for food? Therefore the knowledge implanted in us by God is the mistress and teacher of these things. But it could also be said otherwise: that God, the things which he had commanded, these same he also made [Noah] plainly to know.” Thus far from Chrysostom.⁵

Others think that Moses spoke of this distinction of clean and unclean animals by that figure of speech which is called Anticipation (prolepsis), which is not infrequent in the sacred writings. For God indicated to Noah by name the species of animals from which he should take two each, and the other species from which he should take seven each; but because it afterward came about that, by the law given by God, these were reckoned and called clean and those unclean, therefore Moses — who published this book after the law was given, as Theodoret, Bede, and Tostatus supposed — declared that distinction of animals, in order to indicate it more briefly and clearly, by the distinction of clean and unclean animals already known to the Jews.⁶

It pleases others (and it especially pleases me) that many of the things sanctioned by the law of Moses existed before the law — from the very beginning of the world — in the practice and usage of upright and pious men: such as the building of altars (Gen. 8 and 28), abstinence from blood and from what is strangled (Gen. 9), the making of vows and the offering of tithes (Gen. 28), the raising up of seed for a brother who died without children (Gen. 38); and among these was also this distinction of clean and unclean animals — not indeed as regards eating, for (as will be said later in the ninth chapter) God granted to Noah and his posterity the eating of any animal whatever, without any distinction of clean and unclean, permitting them the eating of animals no less indiscriminately than of vegetables. Therefore, as I said, the distinction of clean and unclean animals in the time of Noah was not in use as regards food, but only as regards the rite and use of sacrifices; and that distin[ction]…⁷

…Noah had received this distinction from the tradition of his ancestors; and if anyone should trace the origin of this tradition to Seth, or to Enos, in whose time men began to invoke the name of God (Gen. 5), I do not know whether he would have strayed from the truth. But the observance of these things was not, before the law of Moses, commanded to men by any precept of God or by a ‘positive’ law (as they call it), but was brought into custom and worship partly by the prompting of God, but chiefly by the tradition of the ancestors.⁸

It has seemed to some that the animals here called clean are those which are naturally suited for human food, while those which are naturally rejected from the eating and diet of men are named unclean. The Gloss, moreover, indicates another cause for this naming, saying that all things are naturally clean, but that some are named unclean by comparison with a better nature: for example, the ox will be called clean, but the lion unclean, because the former is more useful and more serviceable to man for food and clothing and the cultivation of the earth.

Nor must that be passed over which is handed down here by certain Rabbis of the Hebrews — which, however, is not true, and therefore must be refuted by us in passing. They say that all the things commanded to the Jews by the law of Moses had all been observed before the law by upright and pious worshippers of God. They confirm this by several examples, such as those which we set down a little above. But that this is false I will make plain in three matters (lest, by pursuing more where there is no need, I be too long). Jacob took as wives, and had at the same time, two sisters, Leah and Rachel (Gen. 29); but by the law of Moses such a marriage was forbidden to the Hebrews (Lev. 18). God likewise granted to Noah and his posterity the eating of all animals without any distinction, as Moses narrates (Gen. 9); but the law of Moses commanded the Jews to abstain from many kinds of animals as unclean (Lev. 11 and Deut. 14). Finally, Amram, the father of Moses and Aaron, had as wife Jochabed, his cousin — or rather his aunt, that is, his father's sister — as is plainly gathered from the sixth chapter of Exodus and the twenty-sixth of Numbers; yet the law of Moses, as is written in Lev. 18, forbade such a marriage. Therefore not all the things commanded to the Hebrews by the law of Moses were observed before the law by pious men (as those Rabbis trifle).⁹