The Church has always taught that there are two ends of marriage: namely, the procreation of children, and the good of the spouses (unity of the spouses). The ends of the marriage act correspond to these – therefore, every conjugal act must be open to the transmission of human life, and must be performed in a spirit of true respect for the dignity of the other person. The Church teaches that any act which deliberately interferes with the natural end of intercourse is seriously disordered and gravely immoral.
The ends of marriage are inseparable. Contraception and artificial reproductive techniques are both aspects of the objectification of the human person – on the one side, the selfish pleasure of the flesh is put above the dignity of the human person, whilst on the other side, the spouse is used as a means to an end (the begetting of children). In either case, the dignity of the human person created in the image and likeness of God, and the reflection of the life-giving, love-creating union of the Trinity, are obliterated by the selfishness of the individual.
In the words of Saint John Paul II:
“The relationship of the gift changes into a relationship of appropriation”
(St John Paul II, Man and Woman He Created Them: A Theology of the Body, p.260).
“Responsible individuals will quickly see the truth of the Church’s teaching [about contraception], if they consider what consequences will follow from the methods of contraception and the reasons given for the use of contraception. They should first consider how easy it will be to justify behavior leading to marital infidelity or to a gradual weakening in the discipline of morals. Not much experience is needed to understand human weakness and to comprehend that human beings, especially the young, are so susceptible to temptation that they need to be encouraged to keep the moral law. Indeed it is to be feared that husbands who become accustomed to contraceptive practices will lose respect for their wives. They may come to…use their wives as instruments for serving their own desires.”
~ Pope Paul VI ~ in his encyclical Humanae Vitae  pointed to the serious consequences of the use of contraception.
“In destroying the power of giving life, through contraception, a husband and wife is doing something to self. This turns the attention to self and so it destroys the gifts of love in him or her. Once that living love is destroyed by contraception, abortion follows very easily.”
~ Bl. Mother Teresa ~ National Prayer Breakfast, Washington, 4th Feb 1994
The Church and Contraception Mentality
Familiaris Consortio – 1981
John Paul II’s Apostolic Exhortation Familiaris Consortio was the first church document to use the phrase “contraceptive mentality.” Speaking of the situation of the family in the modern world, the pope says:
On the one hand, in fact, there is a more lively awareness of personal freedom and greater attention to the quality of interpersonal relationships in marriage, to promoting the dignity of women, to responsible procreation, to the education of children. There is also an awareness of the need for the development of interfamily relationships, for reciprocal spiritual and material assistance, the rediscovery of the ecclesial mission proper to the family and its responsibility for the building of a more just society. On the other hand, however, signs are not lacking of a disturbing degradation of some fundamental values: a mistaken theoretical and practical concept of the independence of the spouses in relation to each other; serious misconceptions regarding the relationship of authority between parents and children; the concrete difficulties that the family itself experiences in the transmission of values; the growing number of divorces; the scourge of abortion; the ever more frequent recourse to sterilization; the appearance of a truly contraceptive mentality.
Evangelium Vitae – 1995
John Paul II’s Encyclical Evangelium Vitae. Here the pope condemns the use of contraception as a means of lowering abortion rates.
It is frequently asserted that contraception, if made safe and available to all, is the most effective remedy against abortion. The Catholic Church is then accused of actually promoting abortion, because she obstinately continues to teach the moral unlawfulness of contraception. When looked at carefully, this objection is clearly unfounded. It may be that many people use contraception with a view to excluding the subsequent temptation of abortion. But the negative values inherent in the “contraceptive mentality”-which is very different from responsible parenthood, lived in respect for the full truth of the conjugal act-are such that they in fact strengthen this temptation when an unwanted life is conceived. Indeed, the pro- abortion culture is especially strong precisely where the Church’s teaching on contraception is rejected. Certainly, from the moral point of view contraception and abortion are specifically different evils: the former contradicts the full truth of the sexual act as the proper expression of conjugal love, while the latter destroys the life of a human being; the former is opposed to the virtue of chastity in marriage, the latter is opposed to the virtue of justice and directly violates the divine commandment “You shall not kill”.
The Truth and Meaning of Human Sexuality – 1995
Issued by the Pontifical Council on the Family.
Page 92. Through a trusting and open dialogue, parents can guide their daughters in facing any emotional perplexity, and support the value of Christian chastity out of consideration for the other sex. Instruction for both girls and boys should aim at pointing out the beauty of motherhood and the wonderful reality of procreation, as well as the deep meaning of virginity. In this way they will be helped to go against the hedonistic mentality which is very widespread today and particularly, at such a decisive stage, in preventing the “contraceptive mentality”, which unfortunately is very common and which girls will have to face later in marriage.
Page 136. In the first place, parents must reject secularised and anti-natalist sex education, which puts God at the margin of life and regards the birth of a child as a threat. This sex education is spread by large organisations and international associations that promote abortion, sterilisation and contraception. These organisations want to impose a false lifestyle against the truth of human sexuality. Working at national or state levels, these organisations try to arouse the fear of the “threat of over-population” among children and young people to promote the contraceptive mentality, that is, the “anti-life” mentality. They spread false ideas about the “reproductive health” and “sexual and reproductive rights” of young people. Furthermore, some antinatalist organisations maintain those clinics which, violating the rights of parents, provide abortion and contraception for young people, thus promoting promiscuity and consequently an increase in teenage pregnancies. “As we look towards the year 2000, how can we fail to think of the young? What is being held up to them? A society of ‘things’ and not of ‘persons’. The right to do as they will from their earliest years, without any constraint, provided it is ‘safe’. The unreserved gift of self, mastery of one’s instincts, the sense of responsibility — these are notions considered as belonging to another age”.