Concerning the Nature of Good, Against the Manichæans 39
39 Fire is Called Eternal, Not as God Is, But Because Without End PL 42, 563
But fire is eternal, not as God is eternal, because, though without end, yet is not without beginning; but God is also without beginning. Then, although it may be employed perpetually for the punishment of sinners, yet it is mutable nature. But that is true eternity which is true immortality, that is that highest immutability, which cannot be changed at all. For it is one thing not to suffer change, when change is possible, and another thing to be absolutely incapable of change. Therefore, just as man is called good, yet not as God, of whom it was said, "There is none good save God alone;" and just as the soul is called immortal, yet not as God, of whom it was said, "Who alone hath immortality;" and just as a man is called wise, yet not as God, of whom it was said, "To God the only wise;" so fire is called eternal, yet not as God, whose alone is immortality itself and true eternity.
Aeternus ignis dicitur, non sicut Deus, sed quia sine fine. Aeternus autem ignis, non sicut Deus aeternus, quod etsi sine fine sit, non est tamen sine initio; Deus autem etiam sine initio est. Deinde quia licet perpetuus peccatorum suppliciis adhibeatur, mutabilis tamen natura est. Illa est autem vera aeternitas, quae vera immortalitas; hoc est, illa summa incommutabilitas, quam solus Deus habet, qui mutari omnino non potest. Aliud est enim non mutari, cum possit mutari; aliud autem prorsus non posse mutari. Sicut ergo dicitur homo bonus, non tamen sicut Deus, de quo dictum est, Nemo bonus nisi unus Deus ; et sicut dicitur anima immortalis, non tamen sicut Deus, de quo dictum est, Qui solus habet immortalitatem ; et sicut dicitur homo sapiens, non tamen sicut Deus, de quo dictum est, Soli sapienti Deo : sic dicitur ignis aeternus, non tamen sicut Deus, cujus solius immortalitas ipsa est vera aeternitas.