I wrote this some time ago in a comment thread on one of the Patheos atheist blogs. I was thinking of posting it as a reply to one of [edit: username redacted to protect the guilty]’s comments on Walter Einenkel’s diary about “The Question Pro-Life Zealots Cannot Answer," but it's long enough to deserve a diary of its own.
The lives of the potential people who do not exist because the pregnancies that would have produced them were aborted are exactly as valuable as the lives of the potential people who do not exist because the zygotes that would have developed into them were among the ~60% of zygotes that fail to implant, which are exactly as valuable as the lives of the potential people who do not exist because contraception was in use during the acts of sexual intercourse that would otherwise have resulted in their conception, which are exactly as valuable as the lives of the potential people who do not exist because the couples who would have been their parents didn't have sex on the date the sperm and eggs that would have produced them were in place to do so, which are exactly as valuable as the lives of the potential people who do not exist because their potential parents never even met in the first place.
All of which is to say that none of the practically infinite number of lives of potential people who were never born, regardless of the reason why they were never born, carry any moral weight whatsoever, because it isn't our potential that gives our lives value at all. It's our self-awareness: our thoughts, our feelings, our hopes, and, above all, our relationships with other people, who experience grief and loss when we die, that give our lives value and meaning. Those things, not DNA, are the substance of personhood, and a zygote, embryo, or fetus has none of them.
So can a potential life ever have value? Yes: when the woman inside whose body it must develop values it. A wanted pregnancy is a thing of value to the expectant mother, and we should rightly protect it, and mourn its loss if it ends in miscarriage or medically necessary abortion, for her sake, not the potential baby's. Note that this right to assign value to a pregnancy does not extend to the father unless granted to him by the mother: the act of ejaculating inside a woman's vagina does not give a man any ownership interest in her body or any right whatsoever to use her uterus as an incubator of his potential offspring, regardless of whether the sex act was consensual or not. Neither does the act of putting a ring on her finger and reciting marriage vows (or whatever version of a marriage contract and/or ceremony they might use).
The same concept of ownership rights, and lack thereof, also applies to the question of parental consent for abortion. This seems to be a very difficult concept for conservatives to grasp, so I'm going to put it very bluntly and, metaphorically at least, shout it at the top of my lungs: A DAUGHTER IS NOT LIVESTOCK AND HER PARENTS DO NOT HAVE THE RIGHT TO BREED HER. We in the U.S., unlike certain other, less civilized cultures of the present and past, recognize that a minor girl's parents do not have the right to consent to sex on her behalf; we do not allow parents to sell their daughters into prostitution or give them away in marriages not of their choosing, and if they do so we prosecute the buyer/"husband" for rape, and the parents as accessories to rape. We need to recognize that pregnancy and childbirth equally require the consent of the woman or girl inside whose body they take place, and that parents have no more right to consent for their daughters to those dimensions of sex than they do to consent to the act of intercourse.
"But what if [insert your favorite historical hero here] had been aborted?" Then that person would never have lived, and we wouldn't know to miss him or her. Very few of humanity's great achievements were truly dependent on the personality of one particular individual, though. If Mohandas Gandhi, to give an example popular with some of the pro-life nitwits who think this is a knock-down argument, had never been born, there would still have been an Indian independence movement; it just would have had a different spiritual leader. (With any luck, that leader would not have so alienated Jinnah that independence ended up being accompanied by partition and an undeclared civil war in which over a million people were killed and over ten million displaced — but that’s another story for another time.) It's highly likely that the combination of Indian culture and the British desire to see themselves as civilized would even have led to the same successful use of nonviolent, passive resistance tactics, too. If any one of the great scientists and inventors we rightly revere had never been born, somebody else would have discovered or invented the same things they did at around the same time, because the physical laws that make those achievements possible would be no different.
On the other hand, abortion opponents never seem to consider the flip side of this argument: some of the very worst things people have done were the product of a unique personality, and those personalities are disproportionately likely to come from circumstances where abortion would have been a likely outcome. If Ted Bundy's unwed young mother had terminated her pregnancy, it's fantastically unlikely that someone else would have raped and murdered his victims; tragically, she "chose life," or, more likely, had it chosen for her by her deeply religious, brutally abusive father and the fact that in 1946 abortion was not easily available in the U.S. If Adolf Hitler had been aborted, it’s not terribly likely that Anton Drexler’s feckless NSDAP would have succeeded in taking control of the German government; there might still have been a Second World War, as the seeds of that conflict were built into the Treaty of Versailles, but the timing and the key players would have been different, and the German government almost certainly would not have expended any resources on the systematic extermination of Jews and other disfavored civilian populations.
Unlike the pro-lifers, I don't discount the lost potential of the women forced to drop out of college, or never go in the first place, to raise the babies they were prevented from aborting, or pushed into early, unhappy marriages with those babies' fathers. I count the potential of the wanted children never born because their mothers never met the men who would have been their fathers, as they would have if they'd had abortions and continued their educations, more highly than the potential of the unwanted children never born because their mothers had abortions.
I am not quite in that position myself, but close: I exist because my half-sister Christie does not. If Christie had not been born with a congenital heart defect and died at the age of five months, my mother and Christie's father would not have divorced when they did (though my mother is confident they would have divorced eventually, as they really weren't very compatible), my father would not have married my mother, and I would not be typing this; perhaps you would be having this argument with Christie, or with one of the full brothers or sisters she might have had if my mother had stayed longer with her father, or with one of the children my father would have had with whoever he would have married instead of my mother after he and his first wife split up.
Every choice, every event, every possibility realized closes off some lines of possibility while increasing the probability of others. Christie's death was a tragedy for my mother, her then-husband, and their families, but in no possible world do both Christie and I exist. Elective abortion, in general, is no tragedy at all, because nobody suffers an agonizing loss, and the potential opened up by the woman continuing with the life she has chosen, having children when and with whom she wishes to, outweighs the potential closed off by not bending her life to the necessities of an unwanted pregnancy leading to an unwanted child. Medically necessary abortion is a tragedy for the mother (and, often, the father) who have invested time and effort in a wanted pregnancy only to see it fail, but preventing such abortions is a greater tragedy, for the deaths, disabilities, and/or sterility inflicted on the women prevented from having them.