Christians are often accused of being obsessed with sexual sin. Why can’t two people, of whatever sex, do whatever they please in the enclosure of their own room? Who is hurt if a guy wants to get off looking at tantalizing pictures and videos on his computer? What’s the big deal if college students hook up, unhook, and then hook up again with someone? Our jitteriness about sex exposes our prudery and hostility to life. It shows that Christians are all Puritans under the skin.

Faced with these charges, we get defensive and protest that we are equally concerned with other things – with economic evils, with militaristic violence, with the degradation of the environment. We shouldn’t be defensive. We should say that we’re concerned about sexual behavior and norms precisely because of the effect they have on the poor, the way sexual immorality is linked with violence. We should say that we guard God’s commandments regarding sex because violation of those commandments will produce social chaos. Sexual behavior and sexual norms are a key barometer of social health. If things are disordered in our bedrooms, they will be disordered in boardrooms and cabinet offices.

We could make this argument from Romans 1, and many have. I want to make the same point by examining some features of the Levitical system, which shows that sexual fidelity and defense of biblical sexual norms is a critical feature of the church’s calling. We begin at the beginning. Creation is a series of separations, as Yahweh divides light from dark, waters from waters, water from land, day from night (Genesis 1:4, 6, 7, 14, 18; the verb is badal). 

Yahweh later separates (badal) Israel from the nations (Leviticus 20:24) and in so doing forms a new creation. In that new creation, Israel is required to maintain the divisions that Yahweh established. He divides holy and most holy with a veil (Exodus 26:33, the first use of badal since Genesis 1) and Israel’s priests guard the boundary. Priests separate holy and profane, unclean and clean (Leviticus 10:10), and later that burden is placed on all Israel (11:47; 20:24-25).

Separated, they are to maintain separation. The original separation was  an act of creation, so Israel’s maintenance of boundaries of separation is a continuous maintenance of the creation brought into existence by the exodus. To maintain the world God made by separating Israel from Egypt, Israel observes Yahweh’s purity rules, and the way of life laid out in the Torah. Generally, Israel is separated to “love God with your whole heart” (Deuteronomy 6:4-6) a people called to “love your neighbor as yourself” (19:18). Israel maintains her distinctiveness by being a nation characterized by love.

This does not mean that the physical cosmos depends in some “magical” way on Israel’s rituals or obedience. It’s sociological. The new creation is Israel-separated-from-nations, the holy people marked off from the rest, holy places and holy spaces distinguished from profane spaces. That order exists only so long as Israel maintains those separations. When those boundaries are breached and ignored, the established order naturally relapses into undifferentiated chaos. Israel maintains her distinctive way of life in covenant with Yahweh to keep the post-exodus political cosmos in existence.

Sexual practices are among the specific ways Israel maintains this creation. Yahweh begins His instructions about incest by telling Israel, “You shall not do what was done in the land of Egypt where you lived, nor are you to do what is done in the land of Canaan where I am bringing you; you shall not walk in their statutes” (Leviticus 18:3). Separation from Egypt and Canaan includes separation from their sexual conduct and norms of behavior. That is one aspect of the creation Yahweh brought into being in the exodus, and that creation-boundary exists only if Israel remains sexually pure. If Israel begins to imitate Egyptian or Canaanite sexual practices, one of the walls of the creation collapses. Instead of a world of Israel-separated-from-Egypt, we have (as before the exodus) a world where Israel and Egypt are indistinguishable. The firmament cracks, the waters break over the land, and all collapses to chaos.

We can focus this point by observing that each marriage is itself a small cosmos, created by separation. Leviticus 18 prohibits Israelites from “uncovering nakedness” of those who are “flesh of your flesh” (v. 6). A flesh relation may be a strictly biological/genetic relation, the relation a man has with his mother or sister (vv. 7, 9). “Flesh of flesh” relations exist with blood relations of one’s immediate ancestors. An aunt is not a direct ancestor, but she shares flesh with the father, and so she is flesh of flesh (vv. 12-13).

More interestingly, “flesh of flesh” relations exist where there is no biological connection at all. Verse 8 prohibits uncovering nakedness of father’s wife, presumably not one’s mother. Even though a man has no biological relationship with a stepmother, she is still off limits. Verse 14 prohibits uncovering nakedness of one’s father’s brother’s wife. The father has no direct blood relation with this woman – she is his sister-in-law – and she certainly has no blood relation with her nephew. Yet she is treated as “flesh of flesh.” In short, “flesh of flesh” relations include what we can call “covenant flesh” relations. A man and woman unite in one flesh in marriage, and their shared flesh spreads out, as it were, to net the biological relations of each into a flesh-group.

Marriage, according to Genesis 2, requires a “leaving” and “clinging.” What is left behind is an old flesh relation, and what is entered is a relation with new flesh, a new covenant relation. Marriage is like circumcision: It requires the cutting away of the flesh. By the laws of Leviticus, a man can legitimately enter into a one-flesh relation with a wife, only if he has first cut himself off from flesh. Because of this, marriage is creative, an act of separation and reunion. Division and reunion is the pattern of creation in  Genesis 1, and it is the pattern Yahweh follows when He creates Eve from Adam and then tells them to unite again as one flesh. Adam is cut in two, divided from his own flesh, in order to be reunited with Eve.

Each marriage is a fresh cut in the flesh, a new removal from the flesh-group and incorporation in a new flesh-group. Once a new one-flesh relationship is created, once this small-scale cosmos has come into being, it has to be maintained by continuous separation and boundary-guarding. Allowing many men to be one-flesh with my wife produces confusion and chaos. The creation that is a marriage can be maintained only if no one else pulls back the common covering that encompasses husband and wife. That curtain created my marriage; the marriage can continue only if that curtain stays in place. If it is torn, the marriage collapses into confusion.

I’m not indulging in symbol-speak. The confusion that results from breaching the boundaries of marriage is literal: Husbands and wives at war; men thrown into possibly violent rivalry over a woman. Whose child is she carrying? When many of the small worlds of marriage are thrown into confusion, as they are today, the result can only be social pathology on a massive scale.

At another level, the church’s failure to maintain biblical sexual norms puts both the church and the culture in danger. Through Jesus, God has re-created the world again, and a leading feature of the new world is the separation of the church from the world. The church is the holy people of God, and as the holy people the church is called, like Israel, to maintain the boundaries that are constitutive of the new creation. One of the chief boundaries is the difference between Christian and worldly sexual conduct, and sexual expectations and norms. The new creation is church-separated-from-world. Insofar as the church has abandoned God’s commandments regarding sex, to that extent she has weakened the pillars of the world. And the firmament cracks, the stars fall from the sky, and the waters drown the land.

Peter J. Leithart is President of Trinity House.