We sin against our neighbor in four general areas, namely: (1) justice, (2) God’s gift of life, (3) speech, and (4) sexuality.

1. Sins against our neighbor in the area of justice.

The Seventh Commandment of God is, “You shall not steal”, and the Tenth Commandment is, “You shall not covet anything that belongs to your neighbor” (cf. Exodus 20:15, 17; cf. Deuteronomy 5:19, 21).

In the seventh and tenth commandments, God forbids taking or using something that belongs to another against his reasonable wish. Injustices that violate these two commandments are: stealing; borrowing without permission; depriving another of his money or property by deceiving him (fraud); deliberately damaging another person’s good name or property; not paying just debts; not making a reasonable effort to find the owner of an article that we found; depriving a worker of a just wage; wasting an employer’s time, money, or property; cheating; showing unjust or unreasonable anger, hatred, racial prejudice, or unjust discrimination; and depriving one’s family of needed money by gambling, drinking, or foolish spending. If the damage to our neighbor is not serious, the sin is venial.

On a broader plain, all the resources of creation, whether of the mineral, vegetable, or animal worlds, are by their “nature destined for the common good of past, present, and future humanity” (Catechism of the Catholic Church, 2415). Man must not use these resources in a way that ignores his other obligations. For instance, it is sinful to be selfishly concerned only about ourselves and apathetic toward others who need our help. All of the goods of this world come from God. He has given more than enough of them for our use. The material goods that God gives us are not only for ourselves, but also for the benefit of our families and for helping others in need. True happiness comes from doing God’s will. But His will, in most instances, cannot be done without adequate material goods, such as food, clothing, and shelter.

The dominion God gave man over these resources is not absolute. Man is obligated to conserve and preserve them. He must not waste or exhaust them. On the contrary, man must provide for their renewal and replacement.

Anytime that our wrong words or actions encourage another to sin, we become guilty of the sin of scandal, the sin of bad example. The sin is serious if the possible harm we do is serious. It may cause the death of another person’s soul if we lead him to mortal sin.

2. Sins against our neighbor in the area of God’s gift of life.

From the moment of conception until natural death every human being is sacred. With the cooperation of one’s human parents, each person is created by God Himself, in God’s own image and likeness. From the moment of conception, God infuses a spiritual human soul in each person.

Accordingly, the Fifth Commandment of God is: “You shall not kill” (Deuteronomy 5:17, Exodus 20:13). This commandment directs us to respect and care for our bodies and souls and those of our neighbors. God has given us our lives and our bodies as the means to serve Him, to serve ourselves, and to serve our neighbors. In response to His gift, we should take care of our bodies and our health. We should practice moderation and Christian self-discipline in the use of food, alcohol, and tobacco.

Our Lord came to give life, not to take it away. As His followers, we must oppose whatever tends to destroy or abuse human life: murder, suicide, abortion, contraception, euthanasia, drug abuse, drunkenness, fighting, and unjust or unreasonable anger. All of these are contrary to justice, hope, and charity.

Even one’s embryo must be defended in its wholeness. It must be respected, loved and cared for. To the extent of man’s capability, it must be healed when ill or injured. Every human embryo is no less human, no less a person, no less a precious image and likeness of God, no less endowed with every right to life, liberty, and the pursuit of happiness than any other human being.

Similarly, the life and being of every severely injured or diseased, elderly, handicapped or chronically ill person is sacred. Every life must be protected. Intentional euthanasia, in any form and for any motive, no matter how good it seems, is murder. It violates the dignity of the human person and the rights of God, who alone, as the giver of human life, has the right to take a human life.

Christians must do all they can to prevent war and promote the peaceful resolution of international conflicts and aggression. All wars inevitably bring a myriad of evils and injustices, and, except for the right to defend one’s own nation or to help another nation unjustly attacked, they must be avoided whenever possible. We have the duty to defend ourselves and those for whom we are responsible against any unjust aggressor.

3. Sins against our neighbor in the area of speech.

Sins in this area include lying, detraction, and calumny.

The Eighth Commandment of God is: “You shall not bear false witness against your neighbor” (Exodus 20:16; cf. Deuteronomy 5:20). A good name consists in the esteem which people have for a person and the mutual confidence resulting from it. Mutual confidence, based on mutual respect, is the foundation of all family and community life. Without this respect, doubt, mistrust, and suspicion disrupt the family, community, and society.

Every unjustified violation of a person’s good name is a sin. This occurs either when the uncharitable talk is based on truth, which is detraction, or when it is based on a lie, which is calumny. Calumny is the greater sin, because it violates not only justice and love, but also truth.

Revealing the hidden faults of another, gossiping about a person’s known faults, exaggerating his faults, and telling stories about him are ways of damaging a person’s reputation. We are never permitted to tell a lie, because every lie is an abuse of the sacred power which God has given to us. Lies and gossip can start quarrels and discord and may even separate friends and destroy community life.

Priests in particular are bound to strict silence about sins they have heard in the Sacrament of Penance. This is called the sacramental seal of confession. This seal binds the priest under pain of very serious sin and very severe ecclesiastical penalties. It is absolutely sacred and indissoluble. The priest may never, even if threatened with torture and death, reveal or talk about any sin heard in confession without the penitent’s permission, nor may the priest act on his knowledge of such sins or of those who have committed them.

Professional secrets–those learned by doctors, counselors, researchers, employees with respect to their employers, etc.–must also be kept faithfully, although not with as strict an obligation as the sacramental seal of confession.

Confidences one has been entrusted with must not be revealed unless another’s greater rights are at stake, e.g., those who have a right to this knowledge in virtue of their office and responsibilities, such as parents in regard to the well-being of their children or religious superiors with reference to their community members.

4. Sins against our neighbor in the area of sexuality.

The Sixth Commandment of God is: “You shall not commit adultery.” The Ninth Commandment is: “You shall not covet your neighbor’s wife” (Exodus 20:14, 17; cf. Deuteronomy 5:18, 21).

The use of the sexual faculty is a right and privilege of those who are validly married. Therefore, adultery, polygamy, fornication, masturbation, pornography, premarital sex, homosexual practices, indecent entertainment of every description, other acts of impurity, and the fully deliberate lustful desire to commit these acts are all gravely contrary to chastity and are seriously wrong. Though it is impossible to keep all evil thoughts and desires from our minds, we can at least refuse to welcome them. Unwelcome desires, no matter how wrong they seem, cannot defile our hearts as long as we do not consent to them.

All Christians have the responsibility to practice the virtue of chastity according to their state in life, looking to Jesus as their model. The virtue of chastity helps a Christian to regulate the use of his sexual powers according to God’s law. In Baptism, a Christian consecrates his soul and body to Jesus Christ. The procreative faculty, given to us by God as a sacred power, is something holy. It is something good in itself and is important in God’s plan of creation and providence. The misuse of this faculty is evil.

To help foster the virtue of chastity and to overcome the tendency toward lust, we should practice temperance, seek to purify our hearts, behave and dress modestly, and protect others from ideas, actions, and images which are opposed to the Church’s teaching on sexuality.