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Chapter 13: What Sin Is and What It Is Not


Up to this point we have considered free choice and the norms which direct it toward the well-being of persons. Some choices, however, violate moral norms—they are morally evil.1 Since it assumes that in knowing good one sufficiently knows evil, philosophical ethics contains no detailed examination of evil choices. But moral theology must give close attention to evil. For one thing, Christian life is a work of redemption, and redemption is liberation from sin and its effects. For another, a priest is a physician of souls, and sin is the “disease” he treats—although, unlike most diseases, humankind freely afflicts itself with this one.

The present chapter explains what sin is. Because many today give an account of the phenomena of sin incompatible with Christian faith, it also explains with some care what sin is not.

Chapter fourteen treats original sin, which put humankind in the condition of alienation that the redemptive act of Jesus rectifies. Not only do human persons, with the exception of Mary, share the common condition of sin, but also each contributes by his or her personal sins to the evil from which Jesus redeems us. Thus, Jesus not only is the “Lamb of God, who takes away the sin of the world” (Jn 1.29)—that sin in which the whole world shares together—but also is the priest who pours out his own blood “for many for the forgiveness of sins” (Mt 26.28). The sacrifice of Jesus brings acquittal and life to overcome the sin and death first brought into the world by the sin of Adam (see Rom 5.12–18); the blood of Jesus frees us not only from the sin of Adam but from our sins (see 1 Cor 15.3; Rv 1.5; S.t., 3, q. 49, a. 5).

Chapter fifteen explains the different kinds of sin and makes many important distinctions which must be kept in mind if one is to deal effectively with sin in one’s own life and help others deal with it in theirs. Chapter sixteen explains what constitutes grave matter, which is one of the conditions for mortal sin, and criticizes certain theories of “fundamental option.” Chapter seventeen deals with the effects of ignorance, inadvertence, and false conscience on sin and moral responsibility, and also examines sin of weakness. Chapter eighteen clarifies the dynamics by which a Christian can move along the broad and easy road from imperfection through venial sin and mortal sin of various degrees of gravity to eternal damnation.

Unfortunately, although we are redeemed, growth toward perfection is not a smooth process of maturation from imperfect to perfect goodness. Evil remains in us. In this world, each of us must bear this fact constantly in mind: “If we say we have no sin, we deceive ourselves, and the truth is not in us” (1 Jn 1.8). Hence, we must battle against evil throughout this life (see GS 22). We must “lay aside every weight, and sin which clings so closely, and let us run with perseverance the race that is set before us” (Heb 12.1). The fight against sin can require even the shedding of our own blood according to the example of Jesus (see Rv 6.9–11). Having died with Jesus and been raised with him to new life, we now face, by reason of the gift of redemption, the task of destroying the rule of sin in ourselves (see Rom 6). The present treatise on sin is primarily oriented toward this task.

Sins are morally evil acts considered insofar as they disrupt a person’s relationship with God. Not every sin is a choice, but every sin is related to a choice contrary to conscience. In most sins, one does not choose precisely to offend God. Rather, one wrongfully prefers one human good to another human good. Yet by violating moral truth and human good all sins do offend God. Although rooted in the choices of individuals, sins—like choices in general—can be social. Christians must resist attempts to explain away the real evil of sin.

1. In its main lines the treatment of sin in this and the next five chapters depends on St. Thomas Aquinas, to whose work references are supplied where appropriate. The consensus of modern classical moral theology is followed when it consistently develops Thomas and fits into the theological framework of the present work. For a study of a key work of St. Thomas on sin and evil: Carlos Cardona, “Introducción a la questión disputata de Malo: Contribución al diagnóstico de una parte de la situación contemporánea,” Scripta Theologica, 6 (1974), 111–43. For a systematic survey which usefully notes certain problem areas and developments, see Thomas Deman, O.P., “Péché,” Dictionnaire de Théologie Catholique, 12:140–225.