Pope Francis recently made headlines with his discussion of the steps that it might—or might not—be permissible to take to prevent the spread of the Zika virus. Central to his remarks was a comparison between using contraceptives to “avoid pregnancy” so as to avoid passing on Zika to a child, and using contraceptives in an environment in which one faced a high risk of rape. The comparison, however, is misleading: The use of contraceptives by those at risk of rape need not be an act of contraception, whereas the use of contraceptives in the Zika case surely is an instance of contraception.

To act with the intention to prevent procreation is to contracept. Anyone who, foreseeing that his or her action might lead to the conception of a child, takes steps to prevent that possible child from coming to be, has contracepted. This is why one who takes contraceptives in order to prevent transmission of Zika to a baby whom one might otherwise conceive has contracepted: She has used contraceptives in order to prevent the coming to be of a child, so as to prevent the further transmission of the disease. Use of contraceptives in this case “works” by preventing conception.

But the use of contraceptives by rape victims can be different. To explain why, we need the analysis characteristic of double-effect reasoning. If I am deliberating about taking a contraceptive, and believe that contracepting is always wrong, then I must ask myself whether I intend to impede procreation as either an end or a means—and in the event that that effect is not intended, whether there is proportionate reason to accept the procreation-impeding side effect.

Double Effect in the Case of Sexual Assault

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In a case where a woman is the victim of a sexual assault, it is surely permissible for the woman to defend herself against the attack. This is true both before the attack has commenced, if the attacker’s intention is manifest, and so long as the attack continues. Consider, then, her defense against the initiation of the attack, or the attack in its first moments. Following St. Thomas Aquinas, the intention must be only to use force to ward off harm, even if it is foreseen that the force used—the use of a gun, perhaps, or a bat—will have harmful, perhaps even lethal, effects. It is the acceptance of such side effects that the right of self-defense justifies, not the intention of harm to the attacker.

Thus the fact of an unjust attack is not itself sufficient for justifying a possibly lethal defense. Any victim of a violent crime might be tempted to use force not merely to ward off harm but to kill. The Thomistic analysis recognizes such an intention as wrong and the act shaped by this intention as impermissible.

In the case of some violent attacks on the person of another, such as a punch, the attack ceases with the disengagement of the attacker’s body from the victim. In other cases, this is not so: If the attacker has fired a bullet, then even though the attacker is no longer engaged in a bodily way, the bullet works as an extension of the attacker’s body to continue to pose a threat. The victim may, obviously, ward off such extended threats. And in some cases, the extension of attack beyond the disengagement of the attacker’s body is, in fact, carried out by a bodily part of the attacker. Specifically, in the case of rape by a man, the sperm, a part of the attacker, becomes disengaged from the attacker’s body and continues to invade the victim’s bodily integrity.

This form of invasion is unique, for it comes to fruition as an invasion in the same event that sexual intercourse comes to fruition as a one flesh union, namely, the penetration of the ovum by a sperm. This penetration may also be the initiation of a new human life. Many who believe that contraception is immoral do so on the grounds that it is impermissible to do anything intended to prevent or impede the initiation of a new human life. But there is no wrong, it seems, in attempting to prevent or impede that penetration considered precisely as the culmination of an unjust attack.

One might raise the objection that the only reason this further invasion is thought undesirable is precisely because it might lead to a new life. If so, preventing the invasion of the sperm really would be tantamount to an act of contraception. This objection, however, is flawed.

It is true that the significance of the invasion of seminal fluid is shaped by the capacity of the sperm, in conjunction with the ovum, to initiate new human life. That is precisely why the forcible deposit of sperm in the victim’s vagina is so much more grievous an offense than many other forms of violence: Initiating a new human life together is the most profound and intimate of activities that two persons can engage in, and that initiation—the child—is an extension of the personal being of both parties. The attacker’s sperm is thus profoundly invasive precisely in consequence of its reproductive significance.

But this does not bear at all on whether it is the potential new life that is willed against, or the invasion itself. Even the moment of penetration of the ovum by the sperm itself can be understood and accepted, or rejected, under two entirely different descriptions: the initiation of new life, or the culmination of the attack—even if its significance as a culmination is dependent on its significance as life-initiating. An adequate act analysis leaves us with the clear conclusion that an upright agent can only will against the latter.

Contraception is morally impermissible, so our intentions must be upright and not contra-life. Just as it would be impermissible, in defending one’s person against the rapist’s bodily attack, to will him harm or death, so it is impermissible, in defending oneself against the continuation of the attack made by the rapist’s sperm, to will the non-existence of the possible child. To will the non-union of sperm and ovum insofar as that union was the initiation of new life would be to contracept and that is ruled out by Church teaching as intrinsically impermissible. Yet, just as defenders of the doctrine of double effect have held that one can intend only the use of force to defend oneself, so I believe that such defenders can also hold that rape victims can, and should, intend only the repelling or destruction of sperm, or the suppression of ovulation, as a means of defense.

But it seems obvious that in intending such defense, one can accept as a proportionate side effect that a child might well not come into existence. Just as, for serious medical reasons, one may accept infertility as a side effect of the use of contraceptives, similarly, one may accept infertility as a side effect of legitimate self-defense against rape.

Zika Virus

But all this is at a great distance from the topic on which Pope Francis was asked to speak, the use of contraceptives to prevent the conception of children who might be infected by Zika. Whatever his intended meaning, it is clear that such an act would be completely unlike the non-contraceptive acts of victims of rape: It would be an act of contraception, and, if contraception is impermissible, this act would be impermissible as well.

Is there room here for double-effect analysis? If so, then perhaps that is what Francis was indicating in his comparison to the nuns in the Congo. Perhaps the use of contraceptives has as its intention the prevention of disease transmission, with infertility as a side effect.

But if the earlier analysis is sound, there is no such room for double effect. Contraceptives are chosen in the Zika case not because they have a prophylactic effect against the disease, nor because they prevent transmission from mother to child; they are chosen to prevent a child who might suffer from microcephaly from coming into existence.

Thus, Catholics who accept their Church’s teaching on contraception (and others who accept natural law arguments against it) should refrain from using contraceptives in this case. There can, of course, be serious reasons to abstain from sexual intercourse, and the possibility of maternal-fetal transmission of Zika is surely one such reason. Couples concerned about the health of their children should give that serious consideration and in some cases, at least, judge that abstention is the prudent course of action.