Jack, are you ever going to do anything more than troll abortion threads and copy/paste the same post over and over?
It is obvious that both the female egg and the male sperm have a form of life but no one would call either a person. When they unite to form a zygote it certainly is alive. There is a potential person there and a great many people would claim that it actually is a person. Let us grant for a moment that the zygote is a person and let us call that person Mary. I choose a female name since all embryos are female until about the sixth or seventh week.
Now, we all know that a zygote develops into an embryo through the process of cell division. Every now and again the first cell division does not produce a two celled embryo but rather a second zygote --- identical twins. Did Mary suddenly become two persons? Was Mary two persons to begin with? Was Mary even a person to begin with? Let us set those questions aside for the moment and grant that the second zygote is also a person whom we shall call Margaret. It is entirely possible that one or both of these zygotes could divide again to result in triplets, quadruplets, quintuplets etc. The same question applies as to whether one person can became two, three or more persons. When does a person become a person?
These questions might be difficult enough but now it becomes even more complex. Sometimes two eggs are fertilized to form non-identical twins. Once again, let us call them Mary and Margaret. Rarely the two zygotes merge together again to form a two celled embryo. This is called a chimera. Who is this new embryo? Is it Mary or is it Margaret? This new embryo, this chimera, let us call it Mary, develops to term and is born. There is now no question at all that Mary is indeed a person. But here is the odd thing, some of the organs of Mary carry her genes but other organs carry the genes of her twin sister Margaret. So Margaret continues to exist within Mary or perhaps it is Mary within Margaret. Do we have two persons within a single body?
These very serious questions of person-hood arise only if we assume that the soul is infused at conception and that the brand new zygote is fully a person. Is there a more reasonable understanding? I believe there is. Personally I believe that the developing fetus becomes a person only when it is able to survive outside the womb. Sentience occurs at about the same point in the pregnancy very late in the second trimester. For this reason I am against abortion beyond the twentieth week except in very rare extreme circumstances. Otherwise I believe that abortion should be legal, it should be safe, it should be available and it should be the woman’s informed choice but most important of all --- it should be rare. In conclusion, we should always keep in mind that there are no more powerful abortifacients in the world than poverty and ignorance.
I'm glad you acknowledge that human life begins at conception. This, we know as scientific fact. The whole debate over whether abortion is morally permissible or not really does focus on the arbitrary distinction that is created between a human being and a human person.
We know that this distinction between a human being and a human person is subjective. Just look at all the different opinions. You have an opinion, but it's not based on anything objective. You've simply come up with something that makes the most sense to you. Other people disagree with you. Some say first trimester, some say second trimester, some say third trimester, some say viability, some say neuron activity, some say birth (hence partial birth abortions which Clinton supported).
Point is, all these distinctions between a human being and a human person are subjectively created. And this is the key point of importance - The only reason we create a distinction between a human being and a human person is so that we can perform some action to the human non-person that we would otherwise consider immoral. There is no other reason to create the arbitrary distinction.
As for your examples of difficult situations, there is an answer to each one. When we say that "life begins at conception", we are using the term "conception" to mean simply "at its very beginning". For a long time, conception was seen as the ultimate beginning of new human life. But as you've rightly pointed out, sometimes conception (it's very beginning) is different, ie - identical twins.
In the case of identical twins, there was only one human life at conception, but then another human life was formed. In this case, God brought into existence the younger twin by a different method than conception. But it's not a problem. Both their lives as humans had a beginning, and from that beginning they are morally valuable and created in the image of God.
In the case of the Chimera that you describe, such as fraternal twins that end up being one. This is also very simple so long as we hold onto our foundation. The fraternal twins were each unique individuals created in the image of God. Something went wrong. This would happen because there is sin in the world, and things don't always work out perfectly. In your chimera example, we would simply say that one of the humans died, and one of the humans made it. Now, certainly the human that came out was changed and affected by the death of the other, but they still have the same soul they did when they were conceived. Which one made it and which one died? I don't know, and you don't know, but that doesn't affect the principle.
I think the only way to maintain intellectual integrity as a Christian is to be pro-life from conception. We know Biblically that human life is unique amongst all creation and that we alone are created in the image of God, and that all human life is morally valuable. There is no distinction made in Scripture between a human life and a human person. In fact, everything in Scripture, though not 100% specific, would lead one to believe that the life inside a womb is indeed a person, previous discussions of Scripture should highlight that if you followed them.
But even more importantly for me is the scientific position. The distinction between a human person and a human being is a subjective and arbitrary distinction that only exists so that we can perform some action to the non-person human that we would otherwise consider immoral. I have never once heard an argument that shows what I've just said to be wrong. The distinction between a human being and a human person is as unique and subjective as people are unique from each other. The line in the sand between killing a human person and a human being is nothing more than a person's opinion on where they think that line should be. And for me, I would never gamble killing a person over my best guess as to where a fabricated line should be placed.
Otherwise I believe that abortion should be legal, it should be safe, it should be available and it should be the woman’s informed choice but most important of all --- it should be rare.
You really should give Bill Clinton credit when you continually say this. He is the one that coined the phrase - "safe, legal, and rare" when it comes to abortion.