One of the pivotal conceptual keys to the abortion debate is whether and how sex relates to pregnancy. Specifically, are people consenting to pregnancy when they consent to sex? Pro-lifers typically assert a strong and ethically charged relation where consent to sex is a kind of natural invitation to pregnancy. The woman may not willingly or knowingly be inviting pregnancy, especially if the couple is using different kinds contraception, such as condoms and birth-control pills. However, she is still engaging in a sex act, and since contraceptive practices all have a margin of error, she may still get pregnant. If pregnancy should happen, Pro-lifer’s argue, then she now has the responsibility of carrying that child to term–it’s her responsibility which she invited on herself by using nature’s way of making babies. Meanwhile, pro-choicers are liable to argue that sex and pregnancy are divided; having sex is not an invitation to pregnancy. Who is right?

Well, depending on what you mean by “consent” both sides can be right. If consent is understood strictly in terms of knowingly and intentionally desiring non-pregnancy as an outcome of sex, then a woman would not be consenting to pregnancy. We may call that “strict consent.” By this strict sense, consent refers to adult informed consent, that is, reasonably well-informed willful desire for an outcome or against an outcome. This notion entails some combination of expectations, intention, hope or purpose. However there’s another sense wherein consent should either be stretched to include other things than what is specifically desired or the pregnancy should be thought of as a duty-bearing outcome of the consensual sex-act.

Consent to a Forest Fire

Suppose a woman named Elle does not want to start a forest fire, does not expect to start a forest fire, and does not think she will start a forest fire with her actions, yet, she nevertheless applies a lit match to a dry tree along the highway beside a dense Northern Californian forest. She fully understands how fires work, and how that part of California has a propensity for forest fires. She was playing a trick on a friend, Jay, pretending to start a fire but secretly expecting that the match would be blown out by the stiff winds before it touched the wood. She likes playing tricks on her friend Jay. They play tricks on each other, and have fun doing so. She was acting purely for innocent pleasure motives. Unfortunately, despite her intentions, the match did not blow out and the tree immediately caught spark and lit up like a torch. Other trees ensued in the blaze.

Did Elle start a forest fire? Yes. Did she start it knowingly? Yes. Did she intend to start it? No. But is she still legally and ethically culpable for starting that fire? Yes. The responsibility for starting the forest fire falls on her. Her intentions were betrayed by her actions. Put another way, she physiologically consented to the forest fire even if mentally she did not consent to it. She enabled what she did not want. She is morally responsible for enabling it, and it is of secondary importance whether she wanted that outcome or not. She gave a kind of consent.

Consent to Heartburn

Perhaps another illustration would help us understand consent in terms of free consequences. There is a consequential aspect of freedom. People may have the legal and ethical right to conduct themselves in at least a generally “free” way. People may choose their activities, their words, their lifestyle, their vocation, their lovers. But they do not have the liberty to choose whether to accept the consequences (including subsequent responsibilities) of their free actions. No one’s liberty has been violated if they eat a chili cheese dog and receive heartburn, without consent. Heartburn may still occur for people who are prone to acid reflux, and it may even occur for people who take preventive medicine.

In the case of heartburn, no human life hangs in the balance so there’s no ethical quandry about whether to “kill” the heartburn. But there’s still a relevant parallel. No one’s freedom has been violated, nor injustice committed, if the consequences are natural outcomes of freely chosen acts.

Consent to Mothering an Infant

Likewise, a woman may not want her infant child because she stopped consenting to motherhood after the child’s 2nd birthday. But that ship has already sailed. She has no rightful freedom to kill her infant child. Never mind whether she consents to motherhood or not. Birthing a child and being a mother to that child–even if she later refuses consent–is sufficient for establishing a legal duty to care for that child or see that it is surrendered to be cared-for by someone else. Killing the infant is clearly overkill. Consent to the cause is consent to the effect.

Furthermore, even if she never consented to mother the child, she still has a natural consequence and it is not clear (beyond a reasonable doubt) that killing the child (in utero or ex utero) is an ethical option. The human child in utero is now an interested party, whose personal future hangs in the balance. Had this child been the product of rape (an unchosen consequence), or otherwise unjustly introduced, say, through some mad scientist’s experiment, then this line of argument might not follow.

However, as it stands, anyone advocating for some “right” to kill morally and legally guiltless human beings on the basis of someone else’s consent has clearly not satisfied the burden of proof when it comes to deliberating over and administering death sentences.

Physiological Consent

Returning then to the notion of physiological consent, the sex act can be thought of as physiological consent to pregnancy. When two people, capable of conceiving and bearing a child, engage in heterosexual intercourse they are partaking in a physiological invitation for pregnancy. One might say that our bodies are designed or made to make babies this way. Adults should not be surprised if intercourse generates pregnancy. Frankly, this is how people across human history have thought of sex and pregnancy. Sex is the normal, natural, and well-known way for making babies so that if one does not want to make a baby, one should not have sex. If one wants to have sex without making babies, he or she is still responsible if an accidental pregnancy ensues. More recent contraceptive measures and abortion, since 1973, have given people a host of ways to try to divide sex from pregnancy. But if two consenting adults engage in heterosexual intercourse and the sperm and egg meet, and a child is conceived, they have consented to the outcome in the sense of extending the natural means of inviting that consequence.

Thus, the pro-choicer is left with a strict sense of “consent,” consenting to sex does not entail consenting to pregnancy. A person can want one of these and not the other. But this objection isn’t sufficient to discredit the other type of consent. It doesn’t clearly achieve the degree of evidence needed to satisfy the burden of proof (for administering a death sentence). Plenty of doubts remain before one can conclude, beyond a reasonable doubt, that it’s ethically permission to intentionally kill the fetal human being. Meanwhile, this other sort of consent, “physiological sense” remains as a plausible pro-life alternative. Having sex is itself the consent, the invitation, to pregnancy. One can want either or both, but the sex act itself constitutes physiological consent to pregnancy at least insofar as a moral duty ensues as the act itself is a kind of consent irrespective of one’s strict intentions. Likewise, a person who lights a tree on fire has given the relevant kind of consent to starting a forest fire, even if it was an accident.

Pro-lifers, therefore have a few options. Pro-lifers can ague that consent is either not necessary or consent can be physiological such that if a woman gets pregnant because of consensual sex, she is morally culpable for that outcome (i.e., she is morally responsible as a mother to her child). The pro-choicer has to object to the analogies and consider this “physiological consent” either illicit, inadequate, or inapplicable, while doubling down on the more commonly accepted sense of “informed adult consent.”