From the Encyclical Letter Mater et Magistra of Pope John XXIII, May 15, 1961

RESPECT FOR THE LAWS OF LIFE

We must solemnly proclaim that human life is transmitted by means of the family, the family founded on marriage, one and indissoluble, raised for Christians to the dignity of a Sacrament. The transmission of human life is entrusted by nature to a personal and conscious act, and, as such, subject to the all-wise laws of God: laws inviolable and immutable that are to be recognized and observed. Therefore, it is not permissible to use means and follow methods that can be licit for the transmission of plant or animal life.
Human life is sacred: from its very inception, the creative action of God is directly operative. By violating His laws, the Divine Majesty is offended, the individuals themselves and humanity degraded, and likewise the community itself of which they are members is enfeebled.

Gaudeum et Spes 1965

27. Coming down to practical and particularly urgent consequences, this Council lays stress on reverence for man; everyone must consider his every neighbor without exception as another self, taking into account first of all his life and the means necessary to living it with dignity, so as not to imitate the rich man who had no concern for the poor man Lazarus.

In our times a special obligation binds us to make ourselves the neighbor of every person without exception, and of actively helping him when he comes across our path, whether he be an old person abandoned by all, a foreign laborer unjustly looked down upon, a refugee, a child born of an unlawful union and wrongly suffering for a sin he did not commit, or a hungry person who disturbs our conscience by recalling the voice of the Lord, “As long as you did it for one of these the least of my brethren, you did it for me” (Matt. 25:40).

Furthermore, whatever is opposed to life itself, such as any type of murder, genocide, abortion, euthanasia or willful self-destruction, whatever violates the integrity of the human person, such as mutilation, torments inflicted on body or mind, attempts to coerce the will itself; whatever insults human dignity, such as subhuman living conditions, arbitrary imprisonment, deportation, slavery, prostitution, the selling of women and children; as well as disgraceful working conditions, where men are treated as mere tools for profit, rather than as free and responsible persons; all these things and others of their like are infamies indeed. They poison human society, but they do more harm to those who practice them than those who suffer from the injury. Moreover, they are a supreme dishonor to the Creator.

51. To these problems there are those who presume to offer dishonorable solutions indeed; they do not recoil even from the taking of life. But the Church issues the reminder that a true contradiction cannot exist between the divine laws pertaining to the transmission of life and those pertaining to authentic conjugal love.

God, the Lord of life, has entrusted to men the noble mission of safeguarding life, and men must carry it out in a manner worthy of themselves. Life must be protected with the utmost care from the moment of conception: abortion and infanticide are abominable crimes.

Man’s sexuality and the faculty of reproduction wondrously surpass the endowments of lower forms of life; therefore the acts proper to married life are to be ordered according to authentic human dignity and must be honored with the greatest reverence. When it is a question of harmonizing married love with the responsible transmission of life, it is not enough to take only the good intention and the evaluation of motives into account; the objective criteria must be used, criteria drawn from the nature of the human person and human action, criteria which respect the total meaning of mutual self-giving and human procreation in the context of true love; all this is possible only if the virtue of married chastity is seriously practised. In questions of birth regulation the sons of the Church, faithful to these principles, are forbidden to use methods disapproved of by the teaching authority of the Church in its interpretation of the divine law. (1)
Let all be convinced that human life and its transmission are realities whose meaning is not limited by the horizons of this life only: their true evaluation and full meaning can only be understood in reference to man’s eternal destiny.

Pius XI, Encycl. Casti Connubii (1930),

Thou Shalt Not Kill

63. But another very grave crime is to be noted, Venerable Brethren, which regards the taking of the life of the offspring hidden in the mother’s womb. Some wish it to be allowed and left to the will of the father or the mother; others say it is unlawful unless there are weighty reasons which they call by the name of medical, social, or eugenic “indication.” Because this matter falls under the penal laws of the State by which the destruction of the offspring begotten but unborn is forbidden, these people demand that the “indication,” which in one form or another they defend, be recognized as such by the public law and in no way penalized. There are those, moreover, who ask that the public authorities provide aid for these death-dealing operations, a thing which, sad to say, everyone knows is of very frequent occurrence in some places.

64. As to the “medical and therapeutic indication” to which, using their own words, we have made reference, Venerable Brethren, however much we may pity the mother whose health and even life is gravely imperiled in the performance of the duty allotted to her by nature, nevertheless what could ever be a sufficient reason for excusing in any way the direct murder of the innocent? This is precisely what we are dealing with here. Whether inflicted upon the mother or upon the child, it is against the precept of God and the law of nature: “Thou shalt not kill.”50 The life of each is equally sacred, and no one has the power, not even the public authority, to destroy it. It is of no use to appeal to the right of taking away life for here it is a question of the innocent, whereas that right has regard only to the guilty; nor is there here question of defense by bloodshed against an unjust aggressor (for who would call an innocent child an unjust aggressor?); again there is no question here of what is called the “law of extreme necessity” which could never extend to the direct killing of the innocent. Upright and skillful doctors strive most praiseworthily to guard and preserve the lives of both mother and child; on the contrary, those show themselves most unworthy of the noble medical profession who encompass the death of one or the other, through a pretense at practicing medicine or through motives of misguided pity.

65. All of which agrees with the stern words of the Bishop of Hippo in denouncing those wicked parents who seek to remain childless, and failing in this, are not ashamed to put their offspring to death:
“Sometimes this lustful cruelty or cruel lust goes so far as to seek to procure a baneful sterility, and if this fails the foetus conceived in the womb is in one way or another smothered or evacuated, in the desire to destroy the offspring before it has life, or if it already lives in the womb, to kill it before it is born. If both man and woman are party to such practices they are not spouses at all; and if from the first they have carried on thus they have come together not for honest wedlock, but for impure gratification; if both are not party to these deeds, I make bold to say that either the one makes herself a mistress of the husband, or the other simply the paramour of his wife.”51

66. What is asserted in favor of the social and eugenic “indication” may and must be accepted, provided lawful and upright methods are employed within the proper limits; but to wish to put forward reasons based upon them for the killing of the innocent is unthinkable and contrary to the divine precept promulgated in the words of the Apostle: Evil is not to be done that good may come of it.52

67. Those who hold the reins of government should not forget that it is the duty of public authority by appropriate laws and sanctions to defend the lives of the innocent, and this all the more so since those whose lives are endangered and assailed cannot defend themselves. Among whom we must mention in the first place infants hidden in the mother’s womb. And if the public magistrates not only do not defend them, but by their laws and ordinances betray them to death at the hands of doctors or of others, let them remember that God is the Judge and Avenger of innocent blood which cries from earth to Heaven.53

Notes
50. Exod. 20:13, cfr. Decr. S. Offic. May 4, 1897; July 24, 1895; May 31, 1884.
51. St. Augustine, De Nupt. et Concupise., cap. XV.
52. Rom. 3:8.
53. Gen. 4:10.

Roman Catholic Catechism Abortion

2270 Human life must be respected and protected absolutely from the moment of conception. From the first moment of his existence, a human being must be recognized as having the rights of a person — among which is the inviolable right of every innocent being to life.(71)

“Before I formed you in the womb I knew you, and before you were born I consecrated you”. (72)
“My frame was not hidden from you, when I was being made in secret, intricately wrought in the depths of the earth” .(73)

2271 Since the first century the Church has affirmed the moral evil of every procured abortion. This teaching has not changed and remains unchangeable. Direct abortion, that is to say, abortion willed either as an end or a means, is gravely contrary to the moral law:
You shall not kill the embryo by abortion and shall not cause the newborn to perish .(74)
God, the Lord of life, has entrusted to men the noble mission of safeguarding life, and men must carry it out in a manner worthy of themselves. Life must be protected with the utmost care from the moment of conception: abortion and infanticide are abominable crimes.(75)

2272 Formal co-operation in an abortion constitutes a grave offence. The Church attaches the canonical penalty of excommunication to this crime against human life. ‘A person who procures a completed abortion incurs excommunication latae sententiae’ (76) ‘by the very commission of the offence’, (77) and subject to the conditions provided by Canon Law . (78) The Church does not thereby intend to restrict the scope of mercy. Rather, she makes clear the gravity of the crime committed, the irreparable harm done to the innocent who is put to death, as well as to the parents and the whole of society.

2273 The inalienable right to life of every innocent human individual is a constitutive element of a civil society and its legislation:
‘The inalienable rights of the person must be recognized and respected by civil society and the political authority. These human rights depend neither on single individuals nor on parents; nor do they represent a concession made by society and the state; they belong to human nature and are inherent in the person by virtue of the creative act from which the person took his origin. Among such fundamental rights one should mention in this regard every human being’s right to life and physical integrity from the moment of conception until death.'(79)

‘The moment a positive law deprives a category of human beings of the protection which civil legislation ought to accord them, the state is denying the equality of all before the law. When the state does not place its power at the service of the rights of each citizen, and in particular of the more vulnerable, the very foundations of a state based on law are undermined. . . As a consequence of the respect and protection which must be ensured for the unborn child from the moment of conception, the law must provide appropriate penal sanctions for every deliberate violation of the child’s rights.’ (80)

2274 Since it must be treated from conception as a person, the embryo must be defended in its integrity, cared for, and healed, as far as possible, like any other human being.
Prenatal diagnosis is morally licit, ‘if it respects the life and integrity of the embryo and the human foetus and is directed toward its safeguarding or healing as an individual… It is gravely opposed to the moral law when this is done with the thought of possibly inducing an abortion, depending upon the results: a diagnosis must not be the equivalent of a death sentence.’ (81)

2275 ‘One must hold as licit procedures carried out on the human embryo which respect the life and integrity of the embryo and do not involve disproportionate risks for it, but are directed toward its healing, the improvement of its condition of health, or its individual survival.’ (82)
‘It is immoral to produce human embryos intended for exploitation as disposable biological material.’ (83)

‘Certain attempts to influence chromosomic or genetic inheritance are not therapeutic but are aimed at producing human beings selected according to sex or other predetermined qualities. Such manipulations are contrary to the personal dignity of the human being and his integrity and identity’ (84) which are unique and unrepeatable.#