To Florus 4.120
Let us proceed to the rest. Your claim that you assign offenses to the devil, not bodies, has absolutely no force. As I have frequently shown, you are simply denying the facts, with no aim except to avoid the odium of Manichaeus while breathing his poison. Bodies—quite plainly, bodies—are what you assign to the ruler of darkness: you profess their union devilish and accuse their reproductive organs, their movements, and their offspring. Following your earliest instruction, you openly accuse members, not vices. You call devilish the very thing that Manichaeus too resents seeing flourish in the sexes, as I showed from his writings.
To give the reader in brief repetition something he can retain: either show that infants possess will or remove the charge from them. When you fail to do this and instead assert that the devil possesses them because they were generated from bodily union, you show that you assign to the hostile power not sins, which do not exist without will, but bodies themselves. So the lust found in both human beings and animals is natural and instituted by God. But this lust you suffer in the inconsistency of your argument, through which you move among various and opposing doctrines, is conceived no less from stupidity than from impiety. I therefore rightly distinguish Ambrose from your company and do not call him a Manichaean, as you request.
Latin
Verum pergamus ad reliqua. Nihil prorsus valet, quod te ais diabolo reputare, non corpora, sed delicta; inficiaris omnino, sicut frequenter ostendimus, nullo alio studio, nisi ut Manichaei vites invidiam, cuius inspiras venenum. Corpora enim, prorsus corpora reputas principi tenebrarum, quorum commixtionem diabolicam profiteris, quorum genitalia, quorum motus, quorum fructus accusas. Arguis palam ex primo magisterio membra, non vitia; illud enim dicis diabolicum, quod etiam Manichaeus, sicut in scripturis eius docui, in sexibus indignatur vigere. Et ut repetitione brevi lector noster, quod tenere possit, accipiat; aut ostende esse in parvulis voluntatem, aut ab eis crimen amoveto. Quod cum non facis, sed asseris eos propter hoc a diabolo possideri, quia de corporum sunt commixtione generati; ostendis te non peccata, quae sine voluntate non sunt, sed ipsa corpora adversariae potestati deputare. Ut ergo ea libido, quae et in hominibus et in pecoribus invenitur, naturalis et a Deo instituta est; ita ista libido, quam in disputationis tuae varietate perpeteris, per quam inter varia dogmata contrariaque versaris, non minus a stultitia quam a profanitate concepta est. Haud iniuria ergo Ambrosium a vestra cohorte distinguimus; nec illum, sicut petis, Manichaeum vocamus.