Since every human being receives his life from God, every human being has a God-given right to live, and this right involves a corresponding duty on all others to respect that right. Thus, the Moral Law forbids the killing of any human being without the intervention of a legitimate authority. The unborn child, the weakly infant, the unwanted child, the physically or mentally defective, the insane, etc., are all subjects of the Natural Law, and each one possesses the right to life. Consequently, the direct killing of an unborn child, i.e. directly induced abortion, is a crime against Natural and Divine Positive Law. Those also share the guilt who participate in these crimes by their counsel, aid, assistance, or any other means.
Also, the direct application of euthanasia, i.e. the direct compassing of painless death (e.g. by administering an overdose of morphine or any other product) is forbidden by Natural and Divine Positive Law. The direct taking of another life is a crime against the Moral Law, no matter how human or painless the method of killing may be.
Since man is bound to safeguard and protect life, it is lawful to take such means in defense of one's own life as may result in the death or mutilation of an unjust aggressor, i.e. one who has no proper authority to punish. However, the means taken must be in proportion to the danger. That one's defense be without blame, three conditions are required: (1) the danger must be imminent, i.e., simultaneous with the attack; (2) the act of defense may not exceed the force of the attack, inflicting no more damage than is sufficient to ward off the danger; (3) the intention must simply be self-defense, the result to the aggressor - injury or death - being a secondary effect which is permitted, but not intended.
In the interests of the common good, the State has the right by Natural Law to punish and even deprive a person of life as a just punishment for crime committed, since the State has all the means necessary and God's authority to preserve the common good of all: "The ruler is God's minister for good in thy regard, but if thou doest evil, be afraid, for he beareth not the sword in vain." (Rom. 13:4) The necessary authority to inflict such punishment comes from God: "Let every soul be subject to higher powers. For there is no power but from God, and those that are exist by God's arrangement." (Rom. 13:1)
Lynching is forbidden by the Moral Law. The authority to punish or execute a person guilty of crime belongs to the State, and only those who have been properly commissioned may carry out the sentence. Even if a criminal has forfeited his right to life, and is already under judicial sentence of death, no private person or persons may assume authority to carry out the sentence. Lynching is murder.
Legalized sterilization, for the sole purpose of preventing defectives from procreating, is against the Natural Law, for integrity of body is an inalienable right. The State oversteps its authority in inflicting grave mutilation. Such sterilization is also against Divine Positive Law, as Pius XI declares: "Public magistrates have no right over the bodies of their subjects; therefore, where no crime has taken place, and there is no cause present for grave punishment, they can never directly harm or tamper with the integrity of the body, either for reasons of eugenics or for any other reason." (Casti Connubii, §70) The State has authority to punish, but only when crime has been committed. To be defective is not a crime. To have the power of propagating is not a crime. Therefore, the State may not interfere with life or limb of such a person, nor punish (by sterilization) when no crime has been committed.
It is unlawful to expose others to danger to life and health. Since all men have a duty to preserve life, health, and bodily integrity, employers are bound by Natural Law to respect life, health, and integrity of limbs which their employees possess. It is immoral to expose workers to grave danger without proper safeguards. It is also immoral to tax workers beyond their strength, or employ them in work unsuited to their age or sex.
The Moral Law forbids not only the actual committing of all these offenses against the life of others, but forbids likewise all intention and even desire to commit them. Moreover, the indulging in unruly passions, e.g., hatred, anger, revenge, etc., from which serious offences arise, is forbidden by the Moral Law: "Whoever hateth his brother is a murderer." (1 John 3:15) Since hatred is forbidden by the Moral Law, it follows that a Commandment is given of charity and love. Class war is clearly immoral: "Have peace with all men." (Rom. 12:18) Class hatred and class warfare stand condemned by the whole life of our Lord Jesus Christ and by His teaching.
85. Must all men respect the right to life which each individual possesses?
Yes. All men have the duty to respect every human being's right to life.
86. Is it lawful to take away the life of another human being?
The Moral Law forbids the killing of any human being without the intervention of a legitimate authority.
87. What is to be said of euthanasia, as advocated by moderns?
The direct application of euthanasia, i.e. the direct compassing of painless death (e.g. by administering an overdose of morphine or any other product) is forbidden by Natural and Divine Positive Law.
88. Is it lawful to injure or even kill another in self-defense?
It is lawful to take such means in defense of one's own life as may result in the death or mutilation of an unjust aggressor, but the means taken must be in proportion to the danger.
89. Has the State the right to inflict punishment, particularly capital punishment?
Yes. The State has the right and the necessary authority from God to punish and even deprive a person of life as a just punishment for crime committed.
90. Is lynching against the Moral Law?
Yes. Only those properly commissioned by the State may carry out a sentence of punishment or death.
91. What is to be said of legalized or State sterilization of defectives?
Legalized sterilization, for the sole purpose of preventing defectives from procreating, is against the Natural Law and Divine Positive Law.
92. Is it unlawful to expose others to danger of life and health?
Yes, since doing so hinders others in the fulfillment of their duty to preserve life, health, and bodily integrity.
93. Is it only the actual committing of these offenses against the life of others that is forbidden by the Moral Law?
No. The Moral Law forbids not only the actual committing of all these offenses, but forbids likewise all intention and even desire to commit them.