Eternal life is our chief good, and the end of the city of God, of which the Apostle speaks, “And the end everlasting life.” [Rom 6:22] But because eternal life might be understood by those who are not well versed in Holy Scripture, to mean also the life of the wicked, because of the immortality of their souls, or because of the endless torments of the wicked; therefore we must call the end of this City in which the chief good shall be attained, either peace in life eternal, or life eternal in peace, that it may be intelligible to all.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: City of God, book xix, ch. 11