It is sometimes said that only those who live a conjugal life can pronounce on the subject of marriage, and only those who have experienced it can pronounce on love between man and woman. In this view, all pronouncements on such matters must be based on personal experience, so that priests and persons living a celibate life can have nothing to say on questions of love and marriage. Nevertheless they often do speak and write on these subjects. Their lack of direct personal experience is no handicap because they possess a great deal of experience at second-hand, derived from their pastoral work. For in their pastoral work they encounter these particular problems so often, and in such a variety of circumstances and situations, that a different type of experience is created, which is certainly less immediate, and certainly “second-hand,” but at the same time very much wider. The very abundance of factual material on the subject stimulates both general reflection and the effort to synthesize what is known.

That indeed is how this book came about. It is not an exposition of doctrine. It is, rather, the result above all of an incessant confrontation of doctrine with life (which is just what the work of a spiritual advisor consists of). Doctrine—the teaching of the Church—in the sphere of “sexual” morality is based on the New Testament, the pronouncements of which on this subject are brief but also sufficient. It is a marvel that a system so complete can be based on such a small number of statements. Quite obviously, they touch the problem at its most sensitive points, the crucial points which determine all further principles and moral norms. You need only have these few texts to hand—Matthew 5:27, 28, Matthew 19:1-13, Mark 10:1-12, Luke 20:27-35, John 8:1-11, 1 Corinthians 7 (throughout), Ephesians 5:22-33, to form sufficiently clear views on the subject. In the present book (which is not meant as an exercise in exegetics), this handful of most important statements is our frame of reference throughout.

But although it is easy to draw up a set of rules for Catholics in the sector of “sexual” morality the need to validate these rules makes itself felt at every step. For the rules often run up against greater difficulties in practice than in theory, and the spiritual advisor, who is concerned above all with the practical, must seek ways of justifying them. For his task is not only to command or forbid but to justify, to interpret, to explain. The present book was born principally of the need to put the norms of Catholic sexual morality on a firm basis, a basis as definitive as possible, relying on the most elementary and incontrovertible moral truths and the most fundamental values or goods. Such a good is the person, and the moral truth most closely bound up with the world of persons is “the commandment to love”—for love is a good peculiar to the world of persons. And therefore the most fundamental way of looking at sexual morality is in the context of “love and responsibility”—which is why the whole book bears that title.

—Pope John Paul II, in his introduction, written in 1960, to Love and Responsibility