The Substance View
I have given you my own basic argument for the pro-life position. But now I’d like to examine two more arguments, what I consider to be the two strongest arguments for the pro-life position.
Today’s post will focus on a Catholic philosopher, whose argument is grounded in intuitions that most people agree with. My next post will describe an argument by a pro-life atheist; I’ll leave who it is a mystery, but those who are well-read in the abortion issue will likely know who I’m talking about.
Beckwith and the “Substance” View
In his book Defending Life: A Moral and Legal Case Against Abortion Choice, philosopher Frank Beckwith makes an argument that he has deemed the Substance View. His argument is as follows:
1. The unborn entity, from fertilization , is a full-fledged member of the human community.
2. It is prima facie morally wrong to kill any member of that community.
3. Every successful abortion kills an unborn entity, a full-fledged member of the human community.
4. Therefore, every successful abortion is prima facie morally wrong. 
(Frank Beckwith, Defending Life: A Moral and Legal Case Against Abortion Choice, Cambridge: University Press, Cambridge, New York, 2007, p. xii.)
This is an argument I use in my discussions on abortion, as well as my previous argument. In fact, this is the argument that I have adapted my own argument from. Beckwith’s position here relies on the continuum of human essence. In other words, it is morally wrong to kill you now. You are the same entity now as you were in the womb. So it was morally wrong to kill you then, as well.
As I mentioned, Beckwith is a Catholic. So he does believe in the concept of a soul. However, even if you don’t believe in a soul you can at least see that there is a continuity of human essence. You have developed more as a human being, you have developed more skills and basic human abilities (such as the ability to walk, talk, etc.). You have grown taller (perhaps wider). You may have dyed your hair, gotten a piercing or tattoo, broken a bone, gone through puberty, and/or have gone through any number of other changes since you were conceived. But who you are, your substance, hasn’t changed. A substance is simply an entity that maintains its identity through change. The human being is a particular type of substance, a rational, moral agent, and remains one until he/she dies.
Some might argue that we’re not the same entity as we were in the womb because we had no experiences and we have no memory of being in the womb. This argument is mistaken because first, you have no memory of being a newborn or a toddler, either. Yet you are undoubtedly the same entity then as you are now. Second, if your mom had miscarried or aborted you, you would not be here today. The same as if you had died when you were a toddler or newborn. Third, the unborn do have experiences. Even if you don’t consciously remember your experiences, you still have them. The unborn are pushed down the fallopian tubes toward the uterus by tiny hairs called cilia. My friend and pro-life advocate Josh Brahm calls this your first “waterslide ride.” The unborn implants in the uterus. These are all experiences that the unborn have, even if they can’t remember them.
Another objection I occasionally encounter is that our cells die and replace themselves every seven years, so we are not the same person we were seven years ago. However, this doesn’t follow. You are still the same “you” you were seven years ago (and seventeen years ago, and when you were born, and when you were conceived). We all experience changes, but we don’t “cease to exist” every seven years just because our cells replace themselves. The experiences we had before our cells replicated were still had by the same “substance.” Provided we are old enough, we can remember back to times in our lives from before we had our current cells. We may go through changes, but the essence that makes us “us” doesn’t change.
Beckwith has devoted an entire book to defending his argument (and it’s one of the strongest books defending the pro-life position), so obviously it would be impossible to give a full treatment and defense of the argument here. This is the backbone of the argument, and I really think it’s the strongest argument we have (though there are, of course, those who disagree). Beckwith’s argument is made from a non-religious standpoint. Even if you don’t believe in the same theological concepts that he ascribes to, you can’t dismiss the argument simply because it’s made by a Catholic. As he says in his book, if Beckwith’s argument is sound, an atheist, agnostic, or humanist is intellectually obligated to become pro-life. (Beckwith, Defending Life, p. xiv.)
 Beckwith argues from the “moment of conception.” I have changed this to fertilization. Conception is not actually a “moment,” and the process of bringing a human into existence occurs sometime during the fertilization process, even though the exact point has not yet been agreed upon (Beckwith also mentions this later in his book). So I have substituted fertilization because I feel it’s slightly more accurate.
 It should be noted that if the Substance View succeeds, then even unsuccessful abortions are immoral since it is wrong to even attempt to take someone’s life, even if the actual outcome was less than was intended (or if no harm actually arose).
I bet the mystery philosopher is going to be Don Marquis.
If conception is defined as the fertilization process, then of course it's not a "moment," but if it is defined as the point at which a new organism has come into existence, then yes, there is a "moment of conception." See the white paper on when life begins by Maureen Condic. And a moment of conception can be spoken of even if there is not universal agreement as to when (during the fertilization process) that moment is.
I've read Dr. Condic's paper. Fertilization is a process that takes 24-48 hours, and there has been disagreement as to exactly when during that process the human organism comes into being. I believe that Dr. Condic argues as soon as the sperm hits the egg, the new human organism exists. Conception, usually, is spoken of as the point at which the fertilization process is finished (i.e. the unborn organism has been conceived). That entire process takes one to two days, it's not really a moment. If you state the "moment of conception" as the point when fertilization is finished, well, that doesn't exactly answer the question of when the human organism comes into existence (because it happens before the point at which conception is said to have happened).
So perhaps you could tell me what the "moment of conception" is to you?
I may be wrong, but conception seems properly defined as not necessarily the point at which the fertilization process is complete (though it may happen then), but rather the point at which a new human being is conceived — when a new human organism comes into existence (which happens at some point during the fertilization process). So when Beckwith says "the unborn entity, from the moment of conception," he may mean the unborn from the time it came into existence. This seems actually more precise than your revision, since Beckwith is referring to the unborn since it came into existence, whereas you refer instead to the nebulous fertilization process. The question of WHEN the moment of conception happens is not the point here. Beckwith's point in his first premise is that the unborn is a full-fledged member of the human family from the beginning of its existence, whenever in fertilization that might be. (He of course argues for a particular answer to that question.)
But even if conception is defined instead as the completion of the fertilization process (and it does seem in his book like Beckwith might define it this way), it seems that we can still speak of a "moment of conception," as Beckwith does — the moment when the fertilization process ends. On either definition there is a moment of conception.
But that leads in to the problem, because the unborn human exists when it exists, and if it exists before the fertilization process completes, then the "moment of conception" (if conception is defined as the end of the fertilization process) is not when the unborn entity actually comes into existence. I can see your point that if the unborn comes into existence sometime before the fertilization completes, then it makes sense to say that conception has happened at that point.
However, I do try to defer to the experts as much as possible, the embryologists. I have literally dozens of quotes from embryology textbooks that attest to the fact that human beings begin life at fertilization (which makes it incredibly bizarre that pro-choice people continue to contest this). But whenever embryologists speak of human life beginning, they always speak in terms of fertilization, not conception. So that's another reason why I prefer to use the term "fertilization," and not "conception."
My only point, at least initially, was that you were mistaken to say that there's no such thing as a "moment of conception." There is such a moment, even if we define conception as you define it.
My other point, I suppose, is that whether embryologists often use the term conception or not, it may be a useful term to describe the coming into existence of a new organism, especially useful for our purposes (which are different from theirs). On THAT definition it is a more precise term than fertilization. This definition fills a need by capturing in one word something that fertilization doesn't (and I don't know of any other single word that does the job).
It would be good to do a follow up post on the personal identity debate as many PC philosophers will state it isn't whether the fetus is a human being but when it becomes a person. Not to forget for many like Thompson, even it it were that doesn't automatically grant a right to life.
Actually, I'm planning on addressing personhood arguments soon, including addressing the different arguments for personhood proposed by such philosophers as Judith Jarvis Thomson, Mary Anne Warren, Peter Singer, and David Boonin.
Clinton if you can supply the central argument of materialist/functionalists and why a current capacity is needed I'd appreciate it. I've yet to see this stated clearly. Charles Camosy says he deals with it in his latest Peter Singer book.
Will do, Simon. I think David Boonin makes a good case for why a present capacity is needed, and I think Peter Singer also does, as well. I'll be sure and cover that. What I'll probably end up doing is writing an article about why I believe personhood should be established at fertilization, then write a series of articles addressing several pro-choice philosophers and their definitions of personhood, and why their definitions are insufficient and should be rejected.
Aristotle argued that neither conception nor fertilization can occur within time. If conception were an event or change occurring within time A change in time can only occur to something existing in time and therefor no new substance is formed. No substantial form, and there would therefor be no difference between saying "you" exist than saying an ovum and sperm exist in one's parents as teens. In the generation of animal life something new comes into existence. Neat to consider how this reductio ad absurdam dovetails with the Catholic doctrine of special creation which holds , as we see with our free wills and ability to work with non-material objects like mathematics , that simplle biological evolution is not sufficient to explain our being.