There is a recurring argument in the comment threads which claims that some forms of extramarital sex are not prohibited. The argument is that fornication isn’t a biblical concept, and only a small set of defined extramarital sex activities are prohibited:

Adultery. Sex with a woman who is another man’s wife, or sex with a woman who is not your wife (but for this latter definition only if you are married). Sex with a virgin. But after another man has had sex with a virgin, she is fair game unless one of you is married. Sex with prostitutes. Some claim this is only a prohibition against sex with certain kinds of prostitutes (e.g. pagan temple prostitutes). Incest. Bestiality. Homosexuality.

All other forms of sex outside of marriage are then claimed to be permitted. I won’t lay out the entire foundation of faulty logic used to arrive at this claim, but in broad strokes it involves a very narrow reading of the OT, focusing on Leviticus and Exodus, and a tortuously narrow reading of the NT, specifically 1 Cor 6:13-20 (ESV):

13 “Food is meant for the stomach and the stomach for food”—and God will destroy both one and the other. The body is not meant for sexual immorality, but for the Lord, and the Lord for the body. 14 And God raised the Lord and will also raise us up by his power. 15 Do you not know that your bodies are members of Christ? Shall I then take the members of Christ and make them members of a prostitute? Never! 16 Or do you not know that he who is joined[d] to a prostitute becomes one body with her? For, as it is written, “The two will become one flesh.” 17 But he who is joined to the Lord becomes one spirit with him. 18 Flee from sexual immorality. Every other sin[e] a person commits is outside the body, but the sexually immoral person sins against his own body. 19 Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, 20 for you were bought with a price. So glorify God in your body.

I’m not spending time identifying and correcting the long and twisted path of rationalizations used to arrive at the no such thing as fornication claim, because even if the logic used to get there weren’t in fact faulty, 1 Corinthians 7 is sufficient to blow all of these rationalizations out of the water.

7 Now concerning the matters about which you wrote: “It is good for a man not to have sexual relations with a woman.” 2 But because of the temptation to sexual immorality, each man should have his own wife and each woman her own husband. 3 The husband should give to his wife her conjugal rights, and likewise the wife to her husband. 4 For the wife does not have authority over her own body, but the husband does. Likewise the husband does not have authority over his own body, but the wife does. 5 Do not deprive one another, except perhaps by agreement for a limited time, that you may devote yourselves to prayer; but then come together again, so that Satan may not tempt you because of your lack of self-control. 6 Now as a concession, not a command, I say this.[a] 7 I wish that all were as I myself am. But each has his own gift from God, one of one kind and one of another. 8 To the unmarried and the widows I say that it is good for them to remain single, as I am. 9 But if they cannot exercise self-control, they should marry. For it is better to marry than to burn with passion.

What the Apostle Paul explains repeatedly in this passage is that marriage is the solution to sexual temptation. If you don’t desire sex, do not marry. But if you desire sex, the only licit way to pursue it is to marry. And once married, you don’t have the right to refuse sex to your spouse because this would create temptation for sexual immorality.

The text is clear. Marriage is the only permitted path to sex. That we have done great violence to marriage doesn’t (and can’t) change this. However, the fact that we are thwarting God’s plan by destroying marriage should be deeply humbling and convicting. Divorce, child support, and even the subversion of headship are all questions of sexual immorality.

So 1 Cor 7 blows all of the no such thing as fornication rationalizations out of the water at once. But it is even worse for the rationalizers, because their implicit claim is that marriage is the cause of sexual immorality. If no one were married, excluding prostitution homosexuality bestiality incest and sex with virgins, there would be no sexual sin. Every unrelated woman who wasn’t a virgin or a temple prostitute would be fair game for a randy Christian man, so long as neither had married. Christians could be having a giant sexual free for all, if only men and women didn’t marry*. This is not only absurd, but it is the exact opposite of what the Apostle Paul explains is the case. Marriage is the solution to the problem of sexual immorality, but through tortured logic the rationalizers have come to the inescapable conclusion that marriage is the cause of sexual immorality!

I’ll close by noting that Proverbs 5 teaches the same message as 1 Corinthians 7. Verses 1-14 warn the reader to resist the temptation of sexual immorality, or you will fall into the same trap as the speaker:

I did not listen to the voice of my teachers

or incline my ear to my instructors.

14 I am at the brink of utter ruin

in the assembled congregation.”

Then verses 15-19 explain the proper solution to this temptation, before verses 20-23 again remind the reader of the risk if he doesn’t heed the instruction:

15 Drink water from your own cistern,

flowing water from your own well.

16 Should your springs be scattered abroad,

streams of water in the streets?

17 Let them be for yourself alone,

and not for strangers with you.

18 Let your fountain be blessed,

and rejoice in the wife of your youth,

19 a lovely deer, a graceful doe.

Let her breasts fill you at all times with delight;

be intoxicated[d] always in her love.

20 Why should you be intoxicated, my son, with a forbidden woman

and embrace the bosom of an adulteress?[e]

21 For a man’s ways are before the eyes of the Lord,

and he ponders[f] all his paths.

22 The iniquities of the wicked ensnare him,

and he is held fast in the cords of his sin.

23 He dies for lack of discipline,

and because of his great folly he is led astray.

*Non Christians would of course have to do the honors of having sex with virgin women to change their status, but so long as Christians aren’t the ones doing this (according to the rationalization) Christians could engage in an endless orgy without sinning.