City of God - Book 15, Sections 26 & 27
Some might find this strange, but Augustine defends both the literal AND the allegorical interpretation of the Noah story. He believes it was literal history, but was also an allegorical representation of the Gospel. He interprets the presence of both clean and unclean animals on the Ark as symbolizing how both Jews and Gentiles are saved through Christ. He even defends the practice of imaginatively interpreting the entire Old Testament as allegorically prefiguring the stories in the New Testament.
That the ark which Noah was ordered to make figures in every respect Christ and the church.
Moreover, inasmuch as God commanded Noah […] to make an ark, in which he might be rescued from the destruction of the flood, along with his family […] and along with the animals who, in obedience to God's command, came to him into the ark: is certainly a figure of the city of God sojourning in this world; that is to say, of the church, which is rescued by the wood on which hung the Mediator of God and men, the man Christ Jesus. For even its very dimensions, in length, breadth, and height, represent the human body in which He came […].And the other peculiarities of the ark's construction are signs of features of the church.
[…] It may be that one man's exposition excels another's, and that ours is not the best; but all that is said must be referred to this city of God we speak of, which sojourns in this wicked world as in a deluge, at least if the expositor would not widely miss the meaning of the author. […] Or any better interpretation may be given, so long as the reference to this city is maintained. […]
Augustine defends the literal truth of the Noah story and addresses many of the objections it faced, such as how all the animals could fit in the Ark and how they were all fed. In this section, some of what Augustine writes sounds like it could have come straight from a modern Creationist.
Of the ark and the deluge, and that we cannot agree with those who receive the bare history, but reject the allegorical interpretation, nor with those who maintain the figurative and not the historical meaning.
Yet no one ought to suppose either that these things were written for no purpose, or that we should study only the historical truth, apart from any allegorical meanings; or, on the contrary, that they are only allegories, and that there were no such facts at all, or that, whether it be so or no, there is here no prophecy of the church. […]
But they who contend that these things never happened, but are only figures setting forth other things, in the first place suppose that there could not be a flood so great that the water should rise fifteen cubits above the highest mountains […].What reason do they adduce why earth, the heavier and lower element, has for so many ages scaled to the tranquil æther, while water, the lighter, and more likely to ascend, is not suffered to do the same even for a brief space of time?
They say, too, that the area of that ark could not contain so many kinds of animals […]. [Augustine discusses the prodigious dimensions of the Ark.] [W]ho does not see what a capacity these dimensions give to the ark? [All the animals could easily fit in something so large.] For as to their objection that an ark of such size could not be built, it is a very silly calumny; […] they should remember that the ark was an hundred years in building […], an ark which was not made with curved ribs but straight timbers, which was not to be launched by its builders but to be lifted by the natural pressure of the water when it reached it, and which was to be preserved from shipwreck as it floated about rather by divine oversight than by human skill.
While further speculating about Noah’s Ark, Augustine goes so far as to defend allegorical interpretations of his speculations!
Another question is commonly raised regarding the food of the carnivorous animals,—whether, without transgressing the command which fixed the number to be preserved, there were necessarily others included in the ark for their sustenance; or, as is more probable, there might be some food which was not flesh, and which yet suited all. For we know how many animals whose food is flesh eat also vegetable products and fruits, especially figs and chestnuts. What wonder is it, therefore, if that wise and just man was instructed by God what would suit each, so that without flesh he prepared and stored provision fit for every species? And what is there which hunger would not make animals eat? Or what could not be made sweet and wholesome by God, who, with a divine facility, might have enabled them to do without food at all, had it not been requisite to the completeness of so great a mystery that they should be fed? But none but a contentious man can suppose that there was no prefiguring of the church in so manifold and circumstantial a detail. For the nations have already so filled the church, and are comprehended in the framework of its unity, the clean and unclean together, until the appointed end, that this one very manifest fulfillment leaves no doubt how we should interpret even those others which are somewhat more obscure, and which cannot so readily be discerned.