Recently, a pro-life friend of mine witnessed a car displaying two bumper stickers.  The first read “Donate Life, Become a Tissue/Organ Donor,” and the second read “Pro-Choice.”  He commented that he was amused with what he saw as an apparent contradiction, leading a pro-choice friend to chime in, saying that there was no contradiction and that:

[It] makes complete sense. It's the difference between asking someone to do what you believe to be the right thing and the government intruding on your life to demand that you do what some people believe to be the right thing… Asking someone to consider donating tissue and organs (but not demanding it by law) is completely congruent with asking someone to consider carrying their fetus to term (but not forcing them to do so by law).

The issue of abortion is one that divides many liberty-minded people.  Indeed, icons of the libertarian movement seem to fall as far on opposite sides of this issue as one could imagine.  For example, Ron Paul writes in his recent book, Liberty Defined, about his personal experience witnessing an abortion as an OB/GYN resident in the 1960s.  He writes:

I witnessed… the abortion of a fetus that weighed approximately two pounds.  It was placed in a bucket, crying and struggling to breathe, and the medical personnel pretended not to notice.  Soon the crying stopped…

That same day… an early delivery occurred and the infant born was only slightly larger than the one that was just aborted.  But in this room everybody did everything conceivable to save this child’s life.  My conclusion that day was that we were overstepping the bounds of morality by picking and choosing who should live and who should die…

Meanwhile, other libertarian icons like Murry Rothbard fall on the opposite end of the abortion debate.  On the rights of the fetus, Rothbard has argued in Ethics of Liberty:

But what humans, we may ask, have the right to be coercive parasites within the body of an unwilling human host? Clearly no born humans have such a right, and therefore… the fetus can have no such right either.

But Rothbard misses the point of actions, consequences, and responsibility.  I do have a right to be a parasite on a person if that person’s consensual actions resulted in my becoming a parasite.  To return to my earlier example, this is the fundamental distinction to be made between abortion and organ donation.

When my neighbor's kidneys fail (independently of any actions I have taken), it is unfortunate, and I may be moved by compassion to donate one of my kidney's to save his life, but that is my choice.  My neighbor has no right to sustain his life through impositions on my body.  My actions did not contribute to his condition, so I have no legal responsibility for him.

Abortion is a different matter, however, because pregnancy is precipitated by an act of sex.  When that act is consensual (not rape or involving those too young to provide meaningful consent), both individuals have consented to the participation in an action that may often lead to serious consequences. When it does lead to consequences, the question becomes:  Who is legally obligated to take responsibility for those consequences?

Suppose I were to drink and drive, and as a result, I caused an accident that injured another person. There are costs, financial and otherwise, for this accident, so the question is:  Who pays? Me or the victim? The obvious answer, legally and morally, is me: I would be legally responsible for all consequences. It was not my intention to cause a traffic accident, but it was my actions that caused that accident, and therefore it is my legal responsibility to take on all resulting consequences. It would be illegal and immoral to forsake my responsibility because those consequences don't merely disappear; they are left with victim of the accident, who (for the sake of this argument) was completely blameless in his actions but yet is now suffering.

This same principle applies in the case of abortion. When a consensual act between two people leads to an unwanted pregnancy, who pays? The parents or the baby? Abortion in this case is a "passing of the buck," putting the consequences of an action on the innocent who did not consensually participate in the action. We sacrifice one who is not responsible in order to save those who are responsible from the consequences of their consensual action. This is illegal and immoral in the case of drunk driving, why not here?

Of course, this argument does not prohibit abortion in all cases.  In the case of rape, for example, the mother has not given consent in the precipitating action and cannot be held legally responsible for the resulting consequences.  This is one case where the comparison between organ donation and abortion holds true.  Just as cannot be legally required to donate a kidney to a neighbor I have not injured, a mother cannot be legally required to donate her womb to a child she did not consent to conceive.  If a mother has not consented to the action that led to pregnancy, then she would have an absolute legal right to terminate that pregnancy.  Moral questions may still remain, but the legal system should be clear: a raped mother may choose, out of compassion, to bring the child to term (just as one may choose, out of compassion, to donate an organ), but to impose a legal obligation for her to do so would be a gross violation of her consent, autonomy, and liberty.