Today there are many who vindicate the right to sexual union before marriage, at least in those cases where a firm intention to marry and an affection which is already in some way conjugal in the psychology of the subjects require this completion, which they judge to be connatural. This is especially the case when the celebration of the marriage is impeded by circumstances or when this intimate relationship seems necessary in order for love to be preserved.
This opinion is contrary to Christian doctrine, which states that every genital act must be within the framework of marriage. However firm the intention of those who practice such premature sexual relations may be, the fact remains that these relations cannot ensure, in sincerity and fidelity, the interpersonal relationship between a man and a woman, nor especially can they protect this relationship from whims and caprices. Now it is a stable union that Jesus willed, and He restored its original requirement, beginning with the sexual difference. "Have you not read that the Creator from the beginning made them male and female and that He said: This is why a man must leave father and mother, and cling to his wife, and the two become one body? They are no longer two, therefore, but one body. So then, what God has united, man must not divide." [Mt 19:4-6] St. Paul will be even more explicit when he shows that if unmarried people or widows cannot live chastely they have no other alternative than the stable union of marriage: "... it is better to marry than to be aflame with passion." [1 Cor 7:9] Through marriage, in fact, the love of married people is taken up into that love which Christ irrevocably has for the Church, [Eph 5:25-32] while dissolute sexual union [Sexual intercourse outside marriage is formally condemned I Cor 5:1; 6:9; 7:2; 10:8 Eph. 5:5; I Tim 1:10; Heb 13:4; and with explicit reasons I Cor 6:12-20] defiles the temple of the Holy Spirit which the Christian has become. Sexual union therefore is only legitimate if a definitive community of life has been established between the man and the woman.
This is what the Church has always understood and taught, [Cf. Innocent IV, letter "Sub catholica professione," March 6th, 1254, DS 835; Pius II, "Propos damn in Ep Cum sicut accepimus." Nov 13th, 1459, DS 1367; decrees of the Holy Office, Sept 24th, 1665, DS 2045; March 2nd, 1679, DS 2148 Pius XI, encyclical letter "Casti Connubii," Dec 31st, 1930 AAS 22 (1930), pp. 558 559] and she finds a profound agreement with her doctrine in men's reflection and in the lessons of history.
Experience teaches us that love must find its safeguard in the stability of marriage, if sexual intercourse is truly to respond to the requirements of its own finality and to those of human dignity. These requirements call for a conjugal contract sanctioned and guaranteed by society - a contract which establishes a state of life of capital importance both for the exclusive union of the man and the woman and for the good of their family and of the human community. Most often, in fact, premarital relations exclude the possibility of children. What is represented to be conjugal love is not able, as it absolutely should be, to develop into paternal and maternal love. Or, if it does happen to do so, this will be to the detriment of the children, who will be deprived of the stable environment in which they ought to develop in order to find in it the way and the means of their insertion into society as a whole.
The consent given by people who wish to be united in marriage must therefore be manifested externally and in a manner which makes it valid in the eyes of society. As far as the faithful are concerned, their consent to the setting up of a community of conjugal life must be expressed according to the laws of the Church. It is a consent which makes their marriage a Sacrament of Christ.
As has been said above, the purpose of this Declaration is to draw the attention of the faithful in present-day circumstances to certain errors and modes of behavior which they must guard against. The virtue of chastity, however, is in no way confined solely to avoiding the faults already listed. It is aimed at attaining higher and more positive goals. It is a virtue which concerns the whole personality, as regards both interior and outward behavior.
Individuals should be endowed with this virtue according to their state in life: for some it will mean virginity or celibacy consecrated to God, which is an eminent way of giving oneself more easily to God alone with an undivided heart. [Cf. I Cor 7:7, 34; Council of Trent, Session XXIV, can 10 DS 1810; Second Vatican Council, Constitution "Lumen Gentium," 42 43, 44 AAS 57 (1965), pp. 47-51 Synod of Bishops, "De Sacerdotio Ministeriali," part II, 4, b: AAS 63 (1971), pp. 915-916.] For others it will take the form determined by the moral law, according to whether they are married or single. But whatever the state of life, chastity is not simply an external state; it must make a person's heart pure in accordance with Christ's words: "You have learned how it was said: You must not commit adultery. But I say this to you: if a man looks at a woman lustfully, he has already committed adultery with her in his heart." [Mt 5:28]
Chastity is included in that continence which St. Paul numbers among the gifts of the Holy Spirit, while he condemns sensuality as a vice particularly unworthy of the Christian and one which precludes entry into the Kingdom of Heaven. [Cf. Gal 5:19-23; 1 Cor 6:9-11] "What God wants is for all to be holy. He wants you to keep away from fornication, and each one of you know how to use the body that belongs to him in a way that is holy and honorable, not giving way to selfish lust like the pagans who do not know God. He wants nobody at all ever to sin by taking advantage of a brother in these matters... We have been called by God to be holy, not to be immoral. In other words, anyone who objects is not objecting to a human authority, but to God, Who gives you His Holy Spirit." [1 Thess 4:3-8; cf. Col 3:5-7; I Tim 1:10.] "Among you there must not be even a mention of fornication or impurity in any of its forms, or promiscuity: this would hardly become the saints! For you can be quite certain that nobody who actually indulges in fornication or impurity or promiscuity - which is worshipping a false god - can inherit anything of the Kingdom of God. Do not let anyone deceive you with empty arguments: it is for this loose living that God's anger comes down on those who rebel against Him. Make sure that you are not included with them. You were darkness once, but now you are light in the Lord; be like children of light, for the effects of the light are seen in complete goodness and right living and truth." [Eph 5:3-8; cf. 4:18-19.]
In addition, the Apostle points out the specifically Christian motive for practising chastity when he condemns the sin of fornication not only in the measure that this action is injurious to one's neighbor or to the social order but because the fornicator offends against Christ Who has redeemed him with His blood and of Whom he is a member, and against the Holy Spirit of Whom he is the temple. "You know, surely, that your bodies are members making up the body of Christ... All the other sins are committed outside the body; but to fornicate is to sin against your own body. Your body, you know, is the temple of the Holy Spirit, Who is in you since you received Him from God. You are not your own property; you have been bought and paid for. That is why you should use your body for the glory of God." [1 Cor 6:15, 18-20.]
The more the faithful appreciate the value of chastity and its necessary role in their lives as men and women, the better they will understand, by a kind of spiritual instinct, its moral requirements and counsels. In the same way they will know better how to accept and carry out, in a spirit of docility to the Church's teaching, what an upright conscience dictates in concrete cases.