One of the most common mantras of the sexual revolution is that sex is entirely a private act between two consenting adults. As such, there should be no criticism or regulation of what consenting adults do behind closed doors. In other words, what goes on in the privacy of the bedroom stays in the bedroom.
There is certainly some truth in this assertion. After all, sex is not meant to be a public act. Like going to the bathroom or taking a shower, sex is meant to be experienced with privacy.
But it is important not to confuse sex being primarily a private act with sex being merely a private act. Here is the bottom line: it is impossible to separate sex from its public consequences. Even if done in private, sex has public implications. Why? I can think of two reasons.
Public Effect #1: Sexually Transmitted Infections
First, consider the public effects of sexually transmitted infections. According to the CDC, roughly 20 million new sexually transmitted infections occur every year in America, which costs nearly $16 billion in health care costs. Quite obviously, this is an expense that everyone pays for—sexually active or not. And there are also emotional and relational costs to the transmission of STIs as well.
Public Effect #2: Children
The second reason sex is not merely a private act can be summed up in one word: children. By its very nature, sex is a procreative act. It brings another human being (or beings) into existence. Sex is the means by which we populate and fill the earth. Sex does not always result in children, but children cannot come into existence apart from sex (unless, or course, technology is used to circumvent the natural process).
As a speaker and teacher, I have seen many young people who believed their sexual relationships were entirely private, but when the girl gets pregnant they start thinking about their options—marriage, adoption, abortion—which each have unmistakable public consequences.
Interestingly, the public impact of sex is why the state has traditionally cared about marriage. Todd Wilson states it candidly in his book Mere Sexuality:
“I hope you can see now why the state should have no interest in the sexual lives of same-sex couples. It’s precisely because their sexual lives are, as a biological fact, sterile and non-procreative. To put it bluntly, what two people of the same sex choose to do in their bedroom can have no lasting public significance because it cannot bring forth children. Of course, if that were the only concern we faced on this issue, it would be far easier to agree. The push we see today is not for allowance of private acts but for public recognition that seeks to redefine marriage in a way that discounts the procreative power it has to produce children.”
Sex is not merely a private act—it has physical, fiscal, and relational consequences. Let’s stop pretending otherwise.
 I do find it ironic that the very people who proclaim that sex is a private act between consenting adults publicly promote sexual behavior in film, music, social media, and so on. But that is a point for another post.
 Wilson is right about the inability of same-sex relationships to bring forth the next generation. But given the cost of STIs, it doesn’t necessarily follow that the government should have no interest whatsoever as to what same-sex couples—or really any couples—do in the privacy of their homes.
 Todd Wilson, Mere Sexuality (Grand Rapids, MI: Zondervan, 2017), 104.