In this series of columns containing a catechesis on marriage, before we go on to address the final two “hot button” issues current in our time, we need to discuss something very fundamental to marriage and even to the human person. This is the purpose and meaning of the gift of human sexuality.

St. John Paul II, who many believe will be known someday as St. John Paul “the Great,” left us an incredible body of teaching regarding the dignity of the human person, created in the image and likeness of God. Many regard St. John Paul II as the “Pope of the family.” Part of this teaching he gave us is a series of 129 talks at his Wednesday General Audience over a period of five years very early in his pontificate.

This teaching has come to be known as the “Theology of the Body,” but could also be titled “Human Love in the Divine Plan” or “The Redemption of the Body and the Sacramentality of Marriage.” I do not intend to go into an in-depth presentation of this teaching, but for anyone who is interested, it is well worth studying, especially as we try to navigate our way through the questions we face in our day. It was precisely to apply the perennial teaching of the Church to the modern situation of humanity in a new and fresh way that St. John Paul II left us this teaching.

One author described St. John Paul II’s teaching on the theology of the body as a “theological time bomb set to go off, with dramatic consequences, sometime in the third millennium of the Church.” Perhaps that time is now. No Catholic should even think about rejecting the teaching of the Church on human sexuality without considering what St. John Paul II has left us. Of course, no Catholic can legitimately reject the Church’s teaching on faith and morals at any time, as was discussed in a previous column.

The core of this teaching on the theology of the body is that man and woman are created in the image and likeness of God as male and female. This differentiation of the sexes is not “accidental” or insignificant to God’s plan. This difference and complementarity of the sexes is integral to God’s plan for humanity. The sexual complementarity of man and woman really means something, as they are literally made for each other, in their souls but also in their bodies. There is a “language” of the body that a man and a woman “speak” to one another, especially through the sexual union in marriage.

God created human sexuality as something very good and holy, but through the “fall” of Adam and Eve, sin entered into the world, and this original plan and vision for man and woman and the gift of love and sexuality have been disfigured. Even after humanity’s redemption in Christ, the effects of this “original sin” are still with us, and we experience this as concupiscence. We have a weakened human nature that is inclined toward sin. This leads to all kinds of distortions and disordering of the original gift of human sexuality which the human race has experienced through the ages, down to our own day.

The Church very often gets unjustly criticized, even among Catholics, for being negative toward sex or even preoccupied with sexual issues and morality. The exact opposite is true. The Church regards human sexuality as a great gift from God, and as something beautiful, sacred and part of the dignity of the human person. It is not a minor issue when the world takes such a precious treasure and trivializes it and distorts it to be something other than what God created it for. It is part of being a human being, part of the theology of the body.

So, for what did God create human sexuality? For marriage and marriage only, plain and simple. It is made for man and woman, spouses united in marriage, to come together and express their love for one another and potentially bring forth new life, the fruit of their love. It is reflective of the life giving power of God’s love for us.

It sounds strange to have to speak so bluntly and clearly about this, but our culture has so distorted and disfigured this gift of human sexuality that we no longer recognize it for what it is. The “sexual revolution and liberation” movement in the 1960s and 1970s has left us with a tragically impoverished understanding of the dignity of sex. Also, the widespread embracing of the contraceptive mentality, separating sexual love from procreation, has opened the floodgates to all sorts of problems. We live in a culture which says “anything goes” when it comes to sex.

So let us be crystal clear. The only legitimate use of the gift of our sexual nature is within a validly contracted marriage. Only a man and a woman who have entered into the covenant of marriage may engage in the beautiful and life giving experience of sexual union. We call this the “conjugal act” because it is a full expression of marital love and union between spouses, an act which remains always open to life.

Any other use of our sexual powers is morally wrong, according to God’s plan. This includes fornication (sexual activity between persons who are not married), cohabitation (living together as sexual partners without marriage), masturbation (all forms of sexual self-pleasuring), adultery (sexual activity between persons when at least one is married to another), contraception, and homosexual activity (sexual activity between persons of the same sex).

All of these forms of sexual activity are gravely wrong, not because sex is bad, but because sex is so sacred in God’s original plan. They can constitute mortal sin if done with knowledge and the free consent of the will. And this is important and not a trivial matter. What we do in the body is consequential because it is an integral part of who we are as human persons and children of God. It strikes at the heart of who we are as men and women created in God’s own image and likeness.