To Florus 5.21

With similar sharpness you also try to undermine my use of the Gospel testimony that a tree must be known by its fruits. I used it to demonstrate the obvious: marriage cannot be shown good—nor, indeed, the nature replenished through marital activity—or vindicated as God’s work if crimes are said to sprout from it. You replied: ‘Was the Lord speaking about that, rather than about two human wills, the good and the evil? He called the former a good tree and the latter an evil tree, because good works arise from a good will and evil works from an evil one. If we understand marriage as a good tree, we must certainly place fornication opposite it as an evil tree. But if he says that adultery should not be put in the tree’s place there, but rather the human nature from which a human being is born, then here too the tree will not be marriage but the human nature from which a human being is born’ (Augustine, Marriage and Desire 2.26.43).

You are mistaken. The Lord is speaking there not about two wills but about his own person. Although he conferred countless benefits on the Jews, they never stopped accusing him. They could not condemn his works, which they even glorified; nevertheless they charged him with being a Samaritan, full of a demon, and deceiving them by Beelzebul’s spirit (John 8:48; Matthew 12:24). Then the Lord said: ‘Either make the tree good and its fruits good, or make the tree evil and its fruits evil; for a tree is recognized by its fruits’ (Matthew 12:33). That is: either criticize my works, whose goodness is attested by illnesses driven away and health restored, so that you establish my wickedness from the evidence of my works; or, if you do not dare condemn these great benefits, give the good tree—that is, me—the testimony of my fruits. You who praise the benefits must love the benefactor. There, then, Christ commanded that a person be recognized from his works. This rightly supported our teaching that nature and marriage too must be assessed from the quality of their fruitfulness. If the poison of crimes flowed from them, the root too should be judged criminal.

See how blind your understanding is. You thought you could lighten my objection’s weight by placing fornication opposite marriage, so that marriage would appear a good tree and fornication an evil one. Then no fertility should arise from fornication, lest it be proved evil if good marriage were proved by good offspring. But whether a human being is born from marriage or adultery, he proceeds not from shameful conduct but from the nature of seed. The shameful act committed by adulterers’ will does not disturb the arrangements of substance. Nature exercises itself through its own materials. The sin remains with the author of the unlawful will, while innocent offspring comes forth through the creator’s work. You too saw that this answer had to be given. But let the discerning reader attend to how you tried to evade it.

You say: ‘If adultery is not to be placed in the tree’s position there, but human nature from which a human being is born, then here too the good tree will not be marriage but human nature from which a human being is born.’ Here, then, is what you tried to express: just as a human being is not attributed to fornication but to nature, so the sin derived from lawful parents should not be attributed to marriage but to human nature, which the devil infected with an ancient crime. In adulterers, then, you blamed the wanton people’s will, but praised human nature, from which a human being was born even through unlawful intercourse. In lawful parents, however, you praised marriage, from which you deny sin comes, but criticized nature, from which you say a dreadful crime is poured forth.

Let my reader be alert here. If you judged human nature praiseworthy in fornication because it provided the newborn child’s origin unstained by the partners’ shameful acts, how do you condemn that same nature in marriage, saying it provided the cause of natural guilt? You have therefore professed not marriage but human nature to be both a great good and a great evil. What could be more wicked than it, if it engendered crime? What more detestable, if it is possessed by the devil? Let nature attend to whatever skill it has in seed. For the moment, in its quality—the sphere to which every good or evil belongs—it is proved utterly evil if it is itself guilty, produces guilt, and is convicted as the servant of diabolical tyranny. Rightly, then, a tree must be known by its fruits, so that what causes evil is most rightly called evil.