Last week, I compiled a non-exhaustive list of ways that Catholic magisterial teaching has changed. However, I did not explain or substantiate those claims. I would like to begin to do so now.

Today, Pope John Paul II’s “theology of the body” is especially popular among conservative Catholics, at least partially due to the way this school of thought seems to defend traditional Catholic teachings about sex, gender, and family from feminist and pro-LGBT upstarts. But John Paul’s theology of the body reflects magisterial change at least as much as it preserves magisterial continuity.

According to theology of the body, the human body is not merely randomly-assembled matter; it expresses the deeper and more ultimate reality of the person. The body does not simply function; it “speaks.”

This insight structures the way theology of the body approaches sex and gender as well. Male and female bodies, Pope John Paul II claims, are not merely accidents of evolution or means to the end of procreation; they too express a fundamental masculinity or femininity that lives at the level of our personhood.

John Paul II thinks of sexual intercourse in a similar way. Just as male or female body expresses the male or female soul, so sexual intercourse expresses the love between husband and wife. The body expresses the person while sex expresses love.

That good sex ought to express true love may seem obvious and uncontroversial to us, but this way of thinking about the relation between sex and love contradicts what magisterial authorities taught from the time of Augustine until the late nineteenth or early twentieth century.

This Augustinian view of sex, which would be reiterated repeatedly by magisterial authorities over the course of the next millennium and a half, described sex quite differently than we sexual moderns do.

While Augustine and other magisterial authorities recognized the link between marriage and love, they emphatically and explicitly denied that one could have sex with one’s spouse for the purpose of expressing love. Put another way, one could and should love one’s spouse, but one could not have sex with one’s spouse because of that love.

Thus, for the majority of magisterial history, the goods of marriage did not perfectly overlap with the goods of sex. Marriage had purposes that sex lacked.

During this time, magisterial authorities recognized only three morally acceptable reasons to have sex with one’s spouse:

1. In order to procreate
2. In order to prevent oneself from having an affair
3. In order to prevent one’s spouse from having an affair.

Let’s consider these in reverse order.

From Soul-Saving Debt to Love-Making Gift

Until recently, the magisterium taught that married people owed to each other a “spousal debt.” Rather than a gift one freely gave, sex was both a debt one owed and a right one could claim.

Thus, if one spouse felt herself on the verge of succumbing to the temptation of extramarital sex, her husband was duty-bound to provide her an easily accessible sexual outlet.

I ought to mention one important caveat: while the spouse who acquiesced to this request for sex fulfilled his duty and therefore did not sin, the one who requested non-procreative morally prophylactic sex sinned venially.

Yet the magisterium still sanctioned this type of sex. Why?

According to the calculus of salvation, the venial sin of asking for sex with one’s spouse to vent pent up energies supposedly prevented the mortal sin of adultery. It was the sin that paradoxically kept people out of Hell. It was therefore acceptable even if not ideal.

Sex and Procreation

What about sex’s procreative purpose? That married couples have sex with a procreative intent might seem like evidence of magisterial continuity. But contemporary magisterial authorities interpret the procreative potential of sex quite differently than their predecessors did.

Today, married couples simply have to refrain from using artificial birth control when they want to have sex without getting pregnant.

But earlier authorities taught something much more restrictive. Married couples could have sex only if and when they intended to get pregnant. Thus, in contrast to contemporary teachings, which allow married couples to use Natural Family Planning to have sex with the intention of avoiding pregnancy, in earlier eras, married couples were morally obligated to limit sex to those relatively few occasions on which they wanted to conceive.

Therefore, if one knew, for example, that pregnancy was impossible or even unlikely, sexual intercourse would have been forbidden. This explains why Augustine condemned sex during pregnancy: there was simply no way a man could intend to impregnate his already pregnant wife.

Consider how different magisterial teaching about birth control would be if it actually had not changed. Today, scientific advances allow us to pinpoint a woman’s fertile period with much more accuracy than they could in Augustine, Aquinas, or even Alphonsus Liguori’s day.

Rather than the few days a month that a married couple would be required to avoid having sex, a woman’s fertile period would mark the only days a married couple would ever be allowed to have sex.

The implications of this only recently overturned prohibition against expressive sex are even more staggering: what contemporary magisterial authorities encourage–the regulation of child birth through the practice of Natural Family Planning and amorous intercourse–would have been condemned by previous magisterial authorities as mortal sins.

Contemporary Catholics therefore must decide: are Catholics who faithfully practice Natural Family Planning to regulate births mortal sinners, or should the Catholic magisterium sometimes change its mind about even very old teachings?

We cannot answer “no” to both.