For those genuinely interested in understanding.I had recently seen a request on Facebook asking for just this sort of information. The asker, who was a friend of a friend (so I was unable to comment on the thread), seemed earnestly perplexed as to why anyone would think that homosexuality is a sin. That, rather than specifically gay marriage, was his question. I made a general offer on my page to discuss it, and the ensuing thread touched on gay marriage, the authority of the Church, science history—but never actually got around to discussing the question of what makes homosexuality a sin. So I wanted to see what someone else would say.
Given the nature of the discussion following the gay marriage ruling last week, one thing that's clear to me as a Christian who opposes gay marriage is that very few secular people - and sadly, by no means all Christians - really understand why Christians take the position we do.
The post was pretty good as far as it went: basically, "Because homosexual activity is deadly to your soul." I've seen the same sort of thing from a favorite Catholic writer two years ago (he's updated it: Why the Catholic Church Will Never Support Gay Marriage). It's sinful, and sin kills your eternal soul. And we love you, so we don't want that.
The seriousness of sin has been largely lost in today's society. Those who believe in a God of love and forgiveness often cannot conceive of the possibility that he could allow anyone to go to Hell. That's a discussion for another day; but if you have at least a basic understanding what Christians believe about Hell, you can appreciate with Penn Jillette why we take sin seriously.
But neither post addressed homosexuality* per se. How could it be sinful? Unfortunately, all most people hear as an explanation to this question is, "The Bible tells me so." The first author says, correctly, that the Bible reveals that "God intended a natural order for how we would receive and engage in the gift of sexual activity, and it likewise establishes that homosexual sex is outside that established order." That's true, but it's not compelling to people who don't accept the authority of the Bible. Why is there a natural order for sexual activity?
The answer to this is also from the Bible; but it is compelling, not because of any commanding authority, but because of its beauty.
God is love. (1 John 4:8)
So God created mankind in his own image, in the image of God he created them; male and female he created them. (Genesis 1:27)
God saw all that he had made, and it was very good. And there was evening, and there was morning—the sixth day.
Thus the heavens and the earth were completed in all their vast array. (Genesis 1:31–2:1)
And God said, "Be fruitful and multiply, and fill the earth." (Genesis 1:28, and 9:1)
Simply put, God is love; he created us out of love; and he wants more of us to love.
God endowed us, through our sexual function, with the ability to participate in the crown of creation. We do not, even now, fully comprehend the power we hold. A glimpse of it is in the "little death" of lovers' embrace who "feel the earth move." In the world-changing sight of two blue lines. In the first sound of a heartbeat at the doctor's office. Parents especially get that glimpse when they hold that hoped-for child in their arms and look her and each other in the face.
This is humankind at its most Godlike, a power of staggering responsibility. Indeed, it is the recreation of the image of God from Genesis: when a man and a woman engage in the sexual act—that act called "making love"—that makes them "one flesh" (and especially when they conceive a child during this unitive act), the family they create is the fullest possible image—icon—of the Trinity: three persons in one God—Father, Son, and Holy Spirit. And it's not just about making babies. The physical and emotional aspects of sex naturally and deeply bind up those who engage in it. The natural order places sexual activity solidly and solely within the context of marriage to safeguard both that power and the people involved in it.
This concept is called the Theology of the Body, and it actually goes beyond sex to address many aspects of the body, both male and female, in relation to God and each other. Dr. Gregory Popcak, for instance, likes to discuss the theology of the body with regard to attachment parenting. Pope St. John Paul II spoke to women about their "feminine genius" in ways that had nothing to do with the exercise of sex. Catholics are learning how intimately the theology of the body intertwines with the Cross and the Eucharist, the heart of the faith. You can find many authors, speakers, and teachers exploring this concept. Since it's summed up as the nuptial meaning of our physical human forms, which are biologically either male or female, sexuality is at its heart.
The human being, body and soul, was created holy in the image of God. Human sexuality, with its unitive and procreative power, is sacred. Abusing something sacred is not merely sinful; it is the definition of profanity. So that is what the litany of sexual sins in the Bible is about. Every expression of sex (and reproduction, for that matter) that does not take place within the respect, honor, and protect the power of the combined unitive and procreative power of the human body—that is, between a husband and a wife who are open to the possibility of children—is an abuse of sexuality. Homosexual behavior, artificial birth control, premarital sex, in vitro fertilization, adultery: all do violence to the integrity of that sexuality.
This is why this sort of behavior is a sin: because you are sacred and holy, and not to be profaned.
* I always try to begin by clarifying that homosexuality itself is not a sin. We confess that we sin by thought, word, and deed—but not by being.