Many in our society believe the myth that sex is merely a physical thing. It’s just biology. One British sociologist puts it like this:
“Sex is no more a moral issue than eating a good meal. The fact that we eat most meals at home with spouses and partners does not preclude eating out in restaurants to sample different cuisines and ambiences.”
But is that it? Are we just animals? Most of us will admit that intuitively we know that can’t be true.
The Bible actually has a much higher view of sex than our society does. It says that sex isn’t “just physical.” Sex represents a profound union between two people, in which physical oneness is accompanied by oneness in every other area—financial, spiritual, emotional.
That’s why Paul says, “Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body” (1 Cor 6:18). Sex outside of the covenant unity of marriage tears apart a person’s integrity. It literally dis-integrates you.
I’ve been reading a book recently called Hooked. It is a scientific study written by a couple of MDs showing what multiple sexual partners—especially when you’re young—does to your brain. It actually rewires your brain in a way that makes genuine, lasting, selfless relationships much more difficult. They say,
“The individual who goes from sex partner to sex partner is causing his or her brain to mold in such a way that eventually accepts that sexual pattern as normal… The pattern of changing sex partners therefore seems to damage their ability to bond in a committed relationship.”
Another MD summarized some of their findings:
“The kind of attachment damage that occurs after repeated sexual encounters is, in many respects, more pernicious than pregnancy or STD’s, because it typically goes unperceived by affected individuals while causing ongoing difficulties in establishing a lifelong and satisfying relationship.”
The point here is that God’s commands about sex aren’t just arbitrary. God designed each of us as a psychosomatic unity, with mind and body and emotions all bound up together. When we pursue sex outside of His designs, we are literally tearing ourselves apart, “sinning against our own body.”
So when He tells us about the design, remember that He’s doing it for our own good. Many people don’t want to follow God’s design about sex because they’re afraid they will miss out on something; God wants us to follow His design precisely because He doesn’t want us to miss out on something.
 McIlhaney and Bush, Hooked: How Casual Sex is Affecting Our Children, 48. The second quotation is from the a review in the Journal of Human Sexuality by Christopher Rosik: http://narth.com/wp-content/uploads/2011/05/JournalofHumanSexuality_Vol2.pdf