John Cassian, Conferences XVIII–XXIV XIX.15: A question whether chastity ought to be ascertained just as the other feelings

Germanus: As the cure for other ailments, viz., anger, vexation, and impatience, has been shown to consist in opposing to them their contraries, so also we should like to learn what sort of treatment we ought to use against the spirit of fornication: I mean, whether the fire of lust can be quenched by the representation, as in those other cases, of greater inducements and things to excite it: because not merely to increase the incentives to lust within us, but even to touch them with a passing look of the mind, we believe to be utterly fatal to chastity.