Here is the truth about abortion: It kills an unborn baby. We all know this — and with continuing advances in ultrasound technology, it's something we know with greater and greater certainty all the time.

This is one of the things that makes the decision to seek an abortion so emotionally fraught and morally wrenching for most women — because an abortion kills an unborn human being, and we normally believe that human beings possess intrinsic moral dignity or worth and therefore have a right to life, no matter how small or helpless they are.

Of course a baby in the womb differs from most other human beings in residing within and being completely dependent upon another human being with rights of her own. This creates the potential for a tragic, irresolvable moral trade-off between the good of the baby (his or her life) and the good of the pregnant woman (her liberty).

Those who claim a right to abortion respond to this tragic conflict by saying that the government's coercive powers may not be used to force a woman to carry a baby to term against her will. She and no one else is sovereign over her body, including over the human life that resides within it.

But is that sovereignty absolute? As the grotesque scandal swirling around Planned Parenthood has revealed in the starkest terms imaginable, the American approach to defending abortion tends toward a form of absolutism that produces morally monstrous consequences.

It need not be that way. In Europe abortion is legal and easily available nearly everywhere through 12 weeks of pregnancy. After that, countries vary in their restrictions, with most limiting access to abortion as the pregnancy approaches 20 weeks, and a few allowing a woman to terminate a pregnancy as late as 24 weeks — which is right around the time when the baby becomes viable outside the womb.

That makes considerable moral sense. Tacitly acknowledging the tragic trade-offs involved in abortion, it balances the rights of the woman against the rights of the baby. At the start of pregnancy, long before viability, the woman is sovereign. But as the fetus approaches the capacity to survive outside the womb, the woman's sovereignty reaches its limits and her rights give way to those of the baby.

Pro-life activists and moral philosophers, who tend to absolutize the rights of the baby and explain away those of the mother, may this find this an unsatisfying moral muddle. But the European arrangement — which aims to respond truthfully and fairly to the clashing, irresolvable rights claims at the heart of abortion — may well bring us as close as it's possible to get to a political solution.

The American approach to abortion is very different, and far less inclined to accept the need for trade-offs. Ever since Roe v. Wade declared abortion-on-demand a constitutional right, defenders of that right have treated it as absolute, inviolable, and applicable to the entire length of pregnancy, from conception on down to natural birth. But of course that absolutist position can only be rendered morally defensible by denying (against all the contrary evidence) the humanity of the fetus.

And that's where the Planned Parenthood scandal comes in. Want to see the moral consequences of denying that an abortion ends a human life? Watch the videos and listen to people discuss killing and dismembering human bodies, harvesting human organs, and freezing, shipping, and selling them for large sums of money. And listen to these people discuss these matters with about as much reverence as they would otherwise accord a pound of ground beef at the supermarket. (Unless, of course, the person were a vegetarian, in which case the ground beef might well be treated with considerably greater dignity and respect.)

On one level, the urge to deny the humanity of the baby is understandable. Given the equally absolutist instincts of the pro-life movement, defenders of abortion rights fear that conceding that a human life is lost when a pregnancy is terminated could be used as a wedge to outlaw all abortions on "personhood" or other grounds.

But one absolutism doesn't justify another. Especially when anyone capable of reading a sonogram can clearly see that a fetus is a human being, albeit a small and fragile one — and when these same people can watch those Planned Parenthood videos and hear employees of the organization talking about these small and fragile human beings as worthless material to be cut into pieces and sold for gain.

If admitting the humanity of the fetus risks endangering abortion rights, how about the risk of denying that humanity in the face of undeniable contrary facts? (No wonder the videos have defenders of abortion rights in a panic.)

Abortion kills an unborn baby. That is the truth. It's also the firmest foundation on which to ground lasting (if limited) reproductive rights for women.