From a Catholic perspective, marriage is a permanent and exclusive commitment between a man and a woman, who freely give themselves to each other in love and in so doing commit themselves to love and care for any children that may arise from their mutual love. Commitment, intimacy and passion vitalize and nurture covenanted love (Genovesi, 1996). Sexual intimacy is a sign of fully committed love. Outside the context of marriage, genital intimacy, however well intended, is not an expression of total self-giving. Marriage is also a public commitment. The two partners freely choose to enter into this partnership, this covenant. They say 'yes' to each other, to being there for each other and to working together to make God's creative love present in the world. They do this through their active participation in the community as committed partners and through bringing about new life through sexual intercourse. The Catholic perspective on marriage is that it should be treated as something permanent and exclusive in which divorce and extra-marital affairs have no place. Public commitment to a permanent and exclusive partnership of mutual co-operation and self-giving love provides the institutional and community basis for the trust necessary for the married couple to truly open themselves to each other. They are able to give themselves wholly to each other in the knowledge that there is a community who will support them in their decision when times are hard and assist them in the raising of their children.

Marriage is also a Sacrament. In a unique way marriage makes Christ visible in the world through the power of the Holy Spirit. The Second Vatican Council's 1965 Pastoral Constitution of the Church in the Modern World, Gaudium et Spes, explains it like this: For as God of old made Himself present to His people through a covenant of love and fidelity, so now the Savior of men and the Spouse of the Church comes into the lives of married Christians through the sacrament of matrimony. He abides with them thereafter so that just as He loved the Church and handed Himself over on her behalf, the spouses may love each other with perpetual fidelity through mutual self-bestowal. Authentic married love is caught up into divine love and is governed and enriched by Christ's redeeming power and the saving activity of the Church, so that this love may lead the spouses to God with powerful effect and may aid and strengthen them in sublime office of being a father or a mother. For this reason Christian spouses have a special sacrament by which they are fortified and receive a kind of consecration in the duties and dignity of their state. By virtue of this sacrament, as spouses fulfil their conjugal and family obligation, they are penetrated with the spirit of Christ, which suffuses their whole lives with faith, hope and charity. Thus they increasingly advance the perfection of their own personalities, as well as their mutual sanctification, and hence contribute jointly to the glory of God (Gaudium et Spes, para. 48).

Genital Sexual intercourse between a man and a woman has the potential to realise two good things, the unity of the couple and new life. And these two things cannot be separated from each other without diminishing the goodness of sexual intercourse. That is why the best place for sexual intercourse to occur is in the context of marriage. First, genital sexual intercourse is good because it is unitive. The two people grow closer together and become more unified through the extremely intimate act of penetration and ejaculation in the vagina. Sexual intercourse in this sense is not about selfish pleasure but about the complete gift of oneself to the other. Two become one, become unified as one flesh, one mind, and in a certain sense, one spirit. The act of genital sexual intercourse is the culmination and a sign of the trust and love that the two have for each other and their commitment to the idea that God wants a woman and a man to be partners in life, to grow together. Through sexual intercourse the bond of self-giving mutual commitment to each other is renewed and strengthened. But this unitive dimension must also be generative if it to be truly unitive, self-giving, committed, trusting, open to new life and conformed to God's will for humanity and for the couple themselves. Second, genital sexual intercourse is good because it is generative. Put simply, genital sexual intercourse brings about new life. But the meaning given to sexual intercourse in the Catholic perspective is deeper than simple procreation. Clearly, if any two fertile people have sexual intercourse a child could result. The Catholic perspective, however, holds that sex simply for the sake of producing children does not adequately represent God's intended purpose for sexual intercourse because it does not take the unitive dimension into account. The unitive dimension of sexual intercourse emphasises the importance that sex has for humans not merely as a means of reproduction but as a means for fostering loving, trusting and committed relationships that are best suited to raise children. Put simply, a loving committed couple (unitive dimension) is better able to provide a stable and loving environment to raise children (the generative dimension). Moreover, the generative or creative dimension is not limited simply to the biological production of new human beings. Two people who love each other unconditionally and who foster that love through the unitive act of self-giving sexual intercourse are more likely to be open, inclusive and loving towards others. Such a couple are more likely to be committed to working for the good of the community since they are able to rely on the strength that comes from being supported by a loving, trusting, and committed partner.

A Christian understanding of love can be defined as 'seeing as God sees'. The Greek word, which is translated as 'love', in the quote from 1 Cor. 13 above is agape. The word, which appears to be used only in the Bible and appears to connote a particularly Christian conception of love, has its root in the concept of 'to prefer'. Thus, we could understand love in this sense to mean a certain kind of preference or a way of preferring. When I say I 'love' something, I am saying that I 'prefer' that something, that I have a preference for that something. If I say, 'I love sunny days' you understand that I am expressing some sort of preference or appreciation or desire for sunny days. In interpersonal terms, then, to say you love someone is to express a preference for that person. You choose to see that person in a certain way. You choose to will the good of that other person. The Christian understanding of this love, of this way of preferring is described in 1 Cor. 13:4-87. In this letter of St Paul to the early Christian community in Corinth, Paul is giving the Corinthians some advice on certain issues affecting the community. He is saying that to be an effective Christian community certain things are important. These are the things that the Christian community at Corinth should focus on and make a reality in their community. Paul argues that love is more important than any other feature of the Christian community. It is more important than all the other charismatic gifts of the Holy Spirit such as speaking in tongues, prophecy and the like. (Love is more important than even apparently heroic actions such as giving up your possessions or your life. Love is more important than all of the other virtues, even faith and hope. In the end, all that will remain is love. Love is a special kind of preferring. Paul characterizes this special way of preferring as follows: Love is patient; love is kind; love is not envious or boastful or arrogant or rude. It does not insist on its own way; it is not irritable or resentful; it does not rejoice in wrongdoing, but rejoices in the truth. It bears all things, believes all things, hopes all things, endures all things (1 Corinthians 13:4-13). See Pope Francis' reflection on this Pauline text in Amoris Laetitia 90: 118 (2016) In the context of relationships and sexuality education this kind of love, this kind of preferring, defines how we should relate to each other at an interpersonal level as in the general notion of loving your neighbour as yourself. In particular this Pauline understanding of love can be applied to how husband and wife should relate to each other in the specific relationship between a man and a woman in the context of marriage. To illustrate how this might work, try replacing the word love in the text above with the word preferring. What this reveals is that love, in this Christian sense, is not selfish. To prefer is not to possess. Indeed, it is not really even about a 'preference' in the common English sense of something you like. Rather, it is about giving preference to the other, to the beloved. It is about concern for the flourishing, for the wholehearted living of the other, of the beloved one. When I say that I love sunny days, I do not make a claim on them, as if I control or own sunny days, as if sunny days are simply there for my pleasure. Rather, to say that I love sunny days is to be in wonder of sunny days for what they are—sunny, warm, bright. So too when we love someone in this Christian sense there is a certain unconditionality about that love. Our preference is for the person as a person, as he or she is, as the beloved, the one loved. It is about being in wonder of who that person is. In other words, love is about wanting what is good for that person. Love is about wanting that person to flourish, to realise the fullness of their humanity as made in the image of God, male or female. Love in the full sense of the word is a virtue, not just an emotion, and still less a mere excitement of the senses. The virtue is produced in the will and has at its disposal the resources of the will's spiritual potential: in other words, it is an authentic commitment of the free will of one person (the subject), resulting from the truth about another person (Wojtyla, 1981 p. 123).