Augustine, City of God XV.23

The single most influential passage in determining 1 Enoch's exclusion from Western Christian scripture.

Augustine of Hippo (354 – 430 CE) wrote De civitate Dei (The City of God) over thirteen years (413 – 426 CE), partly as a response to the sack of Rome by the Visigoths in 410. Book XV deals with the descent from Adam to Noah — and Augustine has to confront the Watchers tradition directly, since it sits inside the same Genesis 6 his argument is following.

What Augustine has to do

Augustine wants to read the "sons of God" in Genesis 6 as Sethites (the righteous line of Seth) marrying the Cainites (the wicked line of Cain). The moral corruption was cultural, not metaphysical. There were no fallen angels having sex with women. The cosmos stays orderly.

But Tertullian had already argued (see De cultu feminarum) that 1 Enoch's authority is established by Jude 14–15. So Augustine needs to dispose of 1 Enoch as a source — without rejecting Jude.

The argument (XV.23)

Augustine writes:

"We omit, then, the fables of those scriptures which are called apocryphal, because their obscure origin was unknown to the fathers from whom the authority of the true Scriptures has been transmitted to us by a most certain and well-ascertained succession. For though there is some truth in these apocryphal writings, yet they contain so many false statements, that they have no canonical authority. [...]

Let us therefore omit the fables of those scriptures which are called apocryphal, because their obscure origin was unknown to the fathers, and because, by Jews and by the Catholic Church alike, they have not been received into the canon."

Specifically about 1 Enoch:

"We cannot deny that Enoch, the seventh from Adam, wrote some divine things, since the Apostle Jude affirms this in his canonical epistle. But it is not without reason that these are not in the canon of Scripture, which was preserved in the temple of the Hebrew people by the diligence of successive priests. For their antiquity was distrusted, and it could not be ascertained whether they were what Enoch himself had written, since they were not produced by those who would have been the most careful to preserve them according to the regular order of transmission." — De civitate Dei XV.23 (NPNF 2)

What Augustine's argument does

Three moves:

Concedes Jude. Augustine accepts that Enoch wrote something divine, on the apostle's authority. He doesn't have to deny Jude 14–15.
Distinguishes between what Enoch wrote and what we have. The actual text circulating as "1 Enoch" can't be verified as authentic. The chain of transmission is missing. The temple priests didn't preserve it.
Argues from improbable antiquity. If 1 Enoch were really written by the seventh man from Adam, it would predate the flood — and how, Augustine implicitly asks, did such a book physically survive the flood?

This is the canon-determining argument the Western church inherits. Not "1 Enoch is wrong" — rather, "we can't verify it's by Enoch, and the church fathers (whom Augustine elsewhere treats as authoritative) didn't preserve it."

On the Watchers narrative specifically

Augustine then offers his alternative reading of Genesis 6: "sons of God" means sons of Seth (righteous men), and "daughters of men" means daughters of Cain (women from the wicked line). The intermarriage corrupts the godly line. No angels involved. The giants are just unusually large humans, not angel-human hybrids.

This reading — the Sethite interpretation — becomes the dominant Western Christian reading from Augustine through the medieval period and into the Reformation. It supplants the angelic-Watchers reading that had dominated through the third century.

Implications for the reception history

For the Western canon: Augustine's argument from unreliable transmission supplies Western Christianity with a respectable theological reason to exclude 1 Enoch without having to attack Jude or the New Testament's wider use of Enochic imagery (Jude 6, 2 Pet 2:4, 1 Pet 3:19–20).
For interpretation of Genesis 6: The Sethite reading wins. Aquinas, Luther, Calvin, and most Reformation-era commentators follow Augustine.
For the Eastern church: Augustine's authority was less decisive in the East. Greek-speaking and Syriac-speaking Christianity retained more of the Enochic tradition (e.g., 2 Enoch in Slavonic). And in Ethiopia, isolated from Augustinian theology, 1 Enoch stayed scriptural.

Cross-references

Tertullian — the argument Augustine has to answer
Origen — the intermediate position
Genesis 6:1–4 — the disputed passage
Jude 14–15 — the citation Augustine has to handle
Western Christian overview

Augustine, City of God XV.23 — why the Western church rejected 1 Enoch