If you watched the Super Bowl you probably saw, and may even have noticed, the Doritos commercial. It contains a pregnant woman’s ultrasound image of her unborn child. The use of that image provoked a tweet of outrage from NARAL Pro-Choice America:

Now you might call humanizing human fetuses an “anti-choice tactic,” but as an orientation to reality, doing that is hardly controversial. What, then, provokes the outrage from NARAL?

In his 1993 majority opinion in Planned Parenthood v. Casey, Justice Anthony Kennedy wrote: “At the heart of liberty is the right to define one’s own concept of existence, of meaning, of the universe and of the mystery of human life.” Justice Scalia and others have had some rather acerbic things to say about that. But if it’s true, then it’s easy to understand why some would not want to “humanize” a fetus. Easy not only to understand, but to accept. For if people each have the right to “define” their own “concept” of “the mystery of human life,” then somebody who thinks of her fetus not as her baby, but as a clump of cells that may become inconvenient if allowed to develop, has every right to dehumanize it. And those whose mission is to defend that right will naturally take offense if somebody else attempts to humanize the fetus.

The notion that liberty includes such a broad right of definition—along with a presumption that one may act on one’s chosen definitions—was not always so prevalent. Until the Enlightenment, most Western thinkers generally understood liberty or freedom in narrower terms: as the power to act for one’s own reasons within the limits of the natural law (civic law being a reflection of the natural law).

That’s why the American founding fathers could, in the Declaration of Independence, wax eloquent about liberty while appealing at the same time to “the laws of Nature and of Nature’s God” as the ultimate basis of moral norms and human rights. If said laws are thus-and-so and not otherwise, we are not free to define them away for ourselves, but we can be and sometimes are free in the traditional sense. Indeed, without such laws we could not long be free. And in the light of such laws, we ought to have as much political freedom as is consistent with mutual peace.

But if liberty be understood in the Kennedyian sense, there are no such laws to appeal to. The ultimate basis of rights is the dignity of the individual defining for herself what reality is, and acting accordingly.

Among philosophers, that kind of thinking stems from a school of thought known as “voluntarism” (which was also linked to the NARAL reaction here). Voluntarism is the idea that “the will,” whether human or divine, is ultimately self-determining. It need not make its choices in light of such reasons as fixed values or realities in order to be good or free; what makes it good and free, when it is good and free, is that it choose authentically as well as without compulsion. That is the basis of the “choice” defended not only by the pro-choice movement, but by the transgender movement as well. Biologically given realities thus matter far less, for purposes of choice, than one’s own feelings and projects. That’s because, for voluntarists, there are no transcendent values and realities in light of which one’s project of self-definition can be evaluated.

Obviously we can’t evaluate these competing notions of liberty here. But we do need to acknowledge what they are if we are to have a productive conversation in America about the meaning of freedom.