My friend listened, neither smiling nor frowning, as I explained why abortion was an injustice. She waited until I finished. “That’s logical,” she said. “But it doesn’t make sense.”

Never discount “common sense.” It’s what wins the day in politics and policymaking. Your reasoned moral argument, if you have one, has a place, but only as a blueprint. It’s the structure, or form. Unless you join it to matter that people can touch and feel, your logic is for naught, except as an opportunity to show off what a rigorous thinker you are. By itself, it’s of little practical consequence.

The common sense that the pro-life movement brings to the abortion debate is the human instinct to protect the weak, especially the young, or at least to recoil from the thought of inflicting physical harm on them. Take the ancient practice of infant exposure. Parents would abandon their unwanted newborn child outdoors, where he would die or be rescued, perhaps to be enslaved but perhaps to be adopted into a caring family. The biological parents could have strangled or drowned him and disposed of his body, but they didn’t. Their restraint, even if they exercised it primarily to spare their nerves, is of a piece with the pity that might move a compassionate stranger, like pharaoh’s daughter, to save the helpless, harmless bundle of human flesh that was the baby Moses.

The common sense that the abortion-rights movement brings to the debate is, first of all, decency, in the sense of decorum, the impulse to look the other way, to spare our neighbor our undue attention. Pudor, Latin for modesty, particularly a female’s modesty with respect to her body and sexuality, demands from others a reciprocal response. The unborn child whose life the pro-life activist seeks to save is also the pregnancy of a woman whose privacy the pro-choice activist seeks to protect.

Arguments based on privacy mingle with others—we hear stirring words about autonomy, agency, parental rights, freedom of choice—to produce a powerful narrative. From that side of the debate, too, we hear about morality and compassion. Here is a low-income single mother who has responsibilities to her born children as well as to herself. Another mouth to feed would make the family poorer. Moreover, the new child would be born into hardship, increasing the sum of misery in the world.

At that point, our invocation of her unborn child’s right to life can begin to sound like logic-chopping. The decent person is embarrassed to wrangle with her about such a sensitive issue in her personal life. And so we back off from asking her about her tacit assumption that her unborn child has a right to die and that she acts as his natural proxy when she decides to exercise that right for him.

We criticize the lyrics, but the music of her narrative is still appealing. Her story is emotionally effective. By now, it’s rooted deep in our moral imagination, where the notion of a right to die grows next to the commonsense virtue that is respect for our neighbor’s privacy. When the question of a person’s right to die later in life arises, as in our debates over euthanasia and assisted suicide, much ground has already been laid.

To say that a woman who aborts her unborn child honors his putative right to die still sounds off key. More familiar to us is the sense in which she violates his right to life. When we insist that his right to life is absolute, we meet resistance because, in law and popular opinion, the sanctity of everyone else’s right to life is subject to exceptions.

Almost everyone thinks that a person is justified in taking the lives of his neighbors if he does so in self-defense. Many people think that the state is justified in taking the life of a person who has taken the lives of others. Some in the anti-abortion movement happen to maintain that the state has not just the right but a duty to impose capital punishment in such cases. They, together with virtually all of us in the pro-life community, consider the life of an unborn child to be morally equal to that of anyone else. So our critics are correct to point out that at least some of us must think that the doctor or the woman who procured the abortion, or both, should be sent to death row, though we’re embarrassed to say so and, in most cases, even to admit to ourselves where our reasoning leads.

Where our logic dictates capital punishment for abortion, common sense tells us to relent. So we relent. And our critics see that down deep we agree with them that a woman’s pregnancy, the unborn child’s gestation, and the profound, intimate relationship between her and him are sui generis.

We posit, in theory, the sanctity of life and then make exceptions for it: self-defense, capital punishment, and, of course, war. We have reasons for excluding abortion from the list of exceptions, but if we’re to persuade people like my friend who thinks that a ban on abortion would violate common sense, we need to appreciate this complication: She would agree that the right to life is serious and sacred, and the pro-life community on the whole would agree with her that the right is not absolute.

In observance of Memorial Day, another friend, on Facebook, offered this solemn comment: “Regardless of how we may feel about particular conflicts or historical episodes, it is a fact of life that some men (and a few women) are called to pay the ultimate price, for the sake of maintaining our society and way of life.” Some children are so called as well, in the view (though it’s seldom spelled out) of the moderate majority who might restrict or discourage abortion but not prohibit it. They regard it as a serious but necessary price for maintaining our society. Many are the women who regard it as necessary for maintaining their way of life, if not of improving it. To them, we make no more sense than a pacifist does to a soldier on the battlefield—that is, we make some sense, but not common sense.

I say this not to cast doubt on our cause but to explain why the effectiveness of our advocacy is limited. We want skeptics to entertain our arguments. They’re more likely to do so if we entertain their skepticism.