A common argument for abortion is the argument from bodily autonomy. It is reasoned that a woman — and only a woman — has the right to decide how her body is going to be used. If she does not want to share her body with her developing child, she has the right to rid her body of it, even if that requires ending the child’s life. This argument is summed up nicely in a common mantra of abortion-choice advocates, “My body, my choice.”

Much could be said as to why bodily autonomy is not a good justification for abortion rights, but I do not wish to focus on that here. Instead, I want to focus on a tactical approach to exposing the bodily autonomy argument for what it is: a sham. Let me show you how.

Only the most ardent abortion advocates believe in unrestricted abortion throughout all nine months of pregnancy. Most abortion advocates draw the line somewhere, even if they differ on the precise temporal location. Some say abortion is no longer permissible once the baby reaches viability (roughly 23 weeks). Others say the line should be drawn at seven months. Wherever the line is drawn, the fact that a line is drawn between morally permissible and morally impermissible abortions demonstrates that the argument for the moral permissibility of abortion from bodily autonomy is an ad hoc, rather than principled argument. Here’s why.

A woman owns her body during the entire pregnancy. She does not cease to own her body after her baby reaches viability, turns seventh months old, or whatever line one wishes to draw. She owns her body once that line has been crossed, just as she did before that line was crossed. If the justification for abortion is that a woman owns her body, and she owns her body during the entire pregnancy, then to forbid her to choose an abortion at any time during that pregnancy is to violate her bodily autonomy. If she wishes to rid her body of the child, she can do so whenever, and however she wants to if bodily autonomy is an absolute right. If her bodily autonomy can be denied under condition X, then the right to bodily autonomy is not absolute, and thus cannot serve as the ultimate grounding for abortion rights. Bodily autonomy may be normative, but there are circumstances in which it should be superseded by weightier rights/values.

If bodily autonomy is not absolute, such that it can be overruled when the unborn baby reaches condition X, why think it trumps the life of the unborn before the baby reaches condition X? Why does the child’s right to life trump the mother’s bodily autonomy when the child is, say, eight months old, but not when she is three months old? Such questions put the focus where it ought to be: the unborn. If your opponent wishes to make an ontological and/or moral distinction between an early and late fetus, they need to demonstrate exactly how they differ. While there clear functional differences between different stages of fetal development, there is no ontological distinction, and no reason to think that functional differences translate into moral differences.

How would this logic play out strategically in conversation with an abortion advocate? Let me illustrate.

After your opponent has used the argument from bodily autonomy as a justification for abortion, ask:

1. “Are there any abortions you are opposed to?”

If he names some X — and he is likely to do so — ask him to justify that restriction in light of his previous justification for abortion: bodily autonomy. Ask:

2. “Do the bodies of women no longer belong to them when X obtains?”

I would imagine our opponent would respond by quickly acquiescing that the woman’s body still belongs to her, but then add a quick “But!” He will agree that a woman’s body still belongs to her even when X obtains, but the presence of X is sufficient to override her bodily autonomy.

At that point say:

3. “If X can supersede a woman’s bodily autonomy, then bodily autonomy is obviously not absolute, and thus cannot serve as the ultimate justification for abortion rights.”

Go on to ask:

4. “If one’s bodily autonomy can be superseded by X, why can’t one’s bodily autonomy be superseded by the presence of another living human being in her womb?”

He will have to offer up a justification for why X trumps a woman’s bodily autonomy, but Y does not. All of the typical justifications provided (size, level of development/function, degree of dependency, etc.) are morally irrelevant to how we treat human beings.