This interesting missive just over the transom. My responses in blue.
I have been pondering your application of the Potentiality Principle to the question of abortion. It is undoubtedly the case that a one year old child has the potential to become an adult possessing rights-conferring properties. It is also undoubtedly the case, for much the same reasons, that a foetus in the third trimester of pregnancy possesses that same potential. However, as we move back along the chain of causality from childhood to birth to pregnancy and before, at some point we no longer have a potential person.
I agree that at some point we no longer have a potential person. Neither a sperm cell by itself, nor an unfertilized egg cell by itself, nor the unjoined pair of the two is a potential person. See 'Probative Overkill' Objections to the Potentiality Principle. This post refutes the notion that one committed to the Potentiality Principle is also committed to the notion that spermatazoa and unfertilized ova and various set-theoretical constructions of same are also potential persons.
Let the symbol P represent the property of having the potential to possess rights-conferring properties in the future. In order for a thing to possess P, that thing must exist as an entity capable of possessing such a property as P. Now consider a couple of somewhat contrived examples:
1. You have a female friend who is currently dating a man of whom you disapprove. You therefore intervene in order to break up their relationship. If you had not broken up the relationship, they may have gone on to have children together. You have therefore broken a chain of causality that may have culminated in the creation of a child, i.e. an entity possessing P.
However, at the time at which you acted, no such entity existed. I think I am safe in saying that, although your meddling in your friend's relationship may be morally dubious, nobody reasonable would condemn you for murder.
Of course. Murder is wrongful killing of a human. Only what exists and is alive can be killed. (You can't kill a dead man or a refrigerator.) A merely possible x is not an existent x. Hence a merely possible human being cannot be murdered. To prevent a human being from coming into existence is not to commit murder.
2. You are a surgeon in the employ of a state that enforces a policy of eugenics. A woman deemed mentally defective is brought to you to be sterilised. Again, although most people today would have serious qualms about the morality of enforced sterilisation, I don't think they would consider you to be a murderer. You have, with a reasonably high degree of probability, broken a chain of causality that would otherwise have led to the creation of an entity possessing P. But such an entity did not already exist when you acted.
Right. So far, so good.
We can apply the same analysis to the use of contraception such as condoms. Now we are even further along the chain of causality, and it is even more obvious that you are deliberately breaking that chain, but most people would still stop short of convicting you of homicide. We are already in controversial waters though as some people really do consider this homicide (such as those that protested in Spain a few years ago against pharmacists who sell condoms). But it is hard to see how one can reasonably claim that an entity possessing P exists in this situation.
I don't recall the Spain case, but I rather doubt that anyone has ever argued that contraception is a form of homicide. It is perfectly obvious that it is not. But that is not to say that there could not be other arguments against contraception. And of course I agree that "no entity possessing P exists in this situation."
Conception is only different in that there is an apparently single entity, namely the human zygote, to which we can easily point and claim that it possesses P. But ease of identification is of merely pragmatic concern, it carries no logical weight. If you wish to claim that conception represents a fundamentally different situation, the burden is on you to demonstrate that a human zygote is an entity possessing P. It is far from obvious that it is.
Here is where I believe you begin to go wrong. I would say that it is obvious that the two cases are very different and that the burden of proof lies on anyone who thinks they are not. In fact, I find it to be so obvious that they are different that I feel no obligation to argue for the difference; rather, I feel entitled to stand pat unless your side has an argument for no difference. Isn't it spectacularly obvious that there are things that have a potentiality-to-X that their constituents, taken individually, do not have?
It appears to be just one more link in the chain of causality that began when the two potential parents first met (well, actually it presumably began even earlier) and might at some point include the birth of a child. Somewhere along that chain of causation an entity possessing P comes into existence. Why pick fertilisation? Furthermore, since fertilisation is not an atomic act, we still haven't actually answered the question. At which point does the entity come into being? When the sperm first binds to the egg? Why is a zygote a more reasonable choice than an oocyte penetrated by a spermatozoon before genetic fusion has completed?
It seems far more plausible that such an entity does not come into being instantaneously but rather develops gradually. There is no single moment when an entity with the potential to possess rights-conferring properties comes into existence, but rather that potential develops gradually along with the entity. (And there is no single moment when an entity with the potential to possess the potential to possess rights-conferring properties comes into existence either, and so on.)
We can agree that at some point, or rather stage, an entity possessing P comes into existence. Nothing hinges on isolating the exact 'instant' or 'moment' of conception. That is a red herring since one needn't be committed to saying that conception is an instantaneous event. One can cheerfully grant that it is a process that can be divided into stages with the task of dividing it falling to biologists.
The main point I would insist on is that prior to conception there is nothing in existence possessing the potentiality to develop, in the normal course of events, into a rights-bearer, but that after conception there is. That is the crucial difference, and that is the difference that makes the difference between contraception, which is clearly not the killing of a human being, and abortion, which clearly is.
I also disagree when you say that the "potential develops gradually along with the entity." I think that's a mistake. The development of the entity, the conceptus, is the gradual actualization of its potentiality. It is not the potentiality that develops but the thing that has it.
Here is a crude analogy that illustrates some of the main points. A ball of dough has the potential to 'rise.' This potential is not had by any of the ingredients taken individually: the water, salt, flour, yeast. Nor is the potential to rise had by the set or the mereological sum of the ingredients. The potential is had only by the ingredients when properly mixed. Whether or not the potential will be actualized depends, of course, on external conditions such as temperature. But in standard conditions of temperature, atmospheric pressure, etc., the dough will rise. Now this potential does not itself rise or change in any way: it becomes actual or not.
To extend the analogy. Suppose the Anti-Pizza Demon tries to prevent the dough from coming into existence. He places a piece of rubber over the mixing bowl. Has the demon murdered the potential pizza? No. Has he performed a 'pizza abortion'? No. There is nothing there to 'murder.' He has prevented the coming into existence of the dough which has the potential to rise. The Demon has committed 'pizza contraception.'
Anyway, I just thought you might find this interesting. Thank you very much for writing a most stimulating blog.
"I'm a Solipsist, and I must say I'm surprised there aren't more of us." -- Letter received by Bertrand Russell
Thanks for the kind words, Charles. As you can see, I did find your letter interesting.