Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Manichæan Controversy.: Chapter 15

Chapter 15.—The Christian Definition of the Four Virtues.

25.  As to virtue leading us to a happy life, I hold virtue to be nothing else than perfect love of God.  For the fourfold division of virtue I regard as taken from four forms of love.  For these four virtues (would that all felt their influence in their minds as they have their names in their mouths!), I should have no hesitation in defining them:  that temperance is love giving itself entirely to that which is loved; fortitude is love readily bearing all things for the sake of the loved object; justice is love serving only the loved object, and therefore ruling rightly; prudence is love distinguishing with sagacity between what hinders it and what helps it.  The object of this love is not anything, but only God, the chief good, the highest wisdom, the perfect harmony.  So we may express the definition thus:  that temperance is love keeping itself entire and incorrupt for God; fortitude is love bearing everything readily for the sake of God; justice is love serving God only, and therefore ruling well all else, as subject to man; prudence is love making a right distinction between what helps it towards God and what might hinder it. 64

Footnotes

[It would be difficult to find in Christian literature a more beautiful and satisfactory exposition of love to God.  The Neo-Platonic influence is manifest, but it is Neo-Platonism thoroughly Christianized.—A.H.N.]