Human beings are sexual beings. Since our bodies are part of who we are and a vital dimension of the way we exist in, and interact with, the world, our biological makeup as members of a species that procreates through sexual reproduction is of significance when thinking about what it means to be human and how we should best be human. Each human being exists as a specific kind of sexual being. Usually this is as either a male or a female. In the Genesis narratives, we read about how God created human beings, male and female, in God's image. In other words, being male and being female are two ways of being a human body (John Paul II, General Audience, 7 November 1979). Sex education should also include respect and appreciation for differences, as a way of helping the young to overcome their self-absorption and to be open and accepting of others (Pope Francis, 2016 Amoris Laetitia).

Human beings are created for unity. Put bluntly, male genital organs and female genital organs are both necessary for reproduction and no human can procreate alone in any natural way. But this complementarity extends beyond simple physical necessity and compatibility. Rather, as Pope St John Paul II (General Audience, 7 November 1979) has argued in his interpretation of the second Genesis narrative, men and women are better together. In Genesis, God decides that it is not good for the first human being (who arguably has no sexual identity) to be alone. Despite the presence of all the animals the first human being is not happy. So God puts the human being to sleep and creates another human being from the same flesh (the rib) of the first human being. When they awaken, the first human being recognizes the second as 'flesh of my flesh' and expresses, for the first time, joy. In other words, human beings find joy and completion in other human beings. Man and woman find joy and completion in each other. The complementarity of woman and man is characterised by: a) equal dignity; b) significant difference; c) synergetic relation—meaning something more happens when you have woman and man together, e.g. generation of a child or generation of the joy of mutual love; d) intergenerational fruition—in other words the human species and the expression of culture goes on generation after generation after generation across historical time. (Allen, 2014).

Men and Women are fundamentally equal. Man and woman are both human beings. Theologically speaking the creation of human beings precedes the creation of the sexes. Women and men are of equal worth or dignity in the eyes of God. Both male and female are made in God's image and both are called to share in the future God promises. Yet, this fundamental equality does not mean that being a man and being a woman is the same thing. Rather it is equally good to be man as it is to be a woman and neither sex should think of itself as superior in some fundamental or essential way to the other. Man and woman share the same humanity. They are both made in God's image sharing a basic mutuality. Both are called to live in a covenant of love (United States Conference of Catholic Bishops, 1991). Consequently, sexism, that is, the unjust discrimination to the detriment of a person on the basis of his or her sex is not to be tolerated. Since all human beings, whether male or female, share the same dignity or moral worth each gender has an equal claim to the natural human rights that proceed from this worth. Similarly, each gender has a duty to work for the common good and to respect the dignity and rights of others. True, all human beings are not alike from the point of view of varying physical power and the diversity of intellectual and moral resources. Nevertheless, with respect to the fundamental rights of the person, every type of discrimination, whether social or cultural, whether based on sex, race, color, social condition, language or religion, is to be overcome and eradicated as contrary to God's intent (Vatican Council II, Gaudium et Spes, para. 29).