T,

I agree. I am not sure why these arguments are reduced down to “religious believe” and “non-religious”.  Right and wrong is only reserved for those who believe in God? Issues of social justice? I suspect it’s merely a rationalization: “oh, only those religious fanatics who are too dopey to think for themselves believe abortion is wrong, and I am not one of those, therefore, I can believe in abortion.” In many cases, such as obvious acts against the innocent such as abortion, religion just reinforces right and wrong, not dictates it.

I would suppose my reasoning goes as such: I do not think the comparison you’ve made between acorns to oak trees; fetuses to humans is valid.  I would agree with you that a gamete is not a human being; it is, if you’re going to really stretch language, a potential child. But a fetus is not a potential child, it is a human being. Human beings, by definition (until RvW) are those beings developing towards the point of death, with a biologically unique identity. I just don’t see what is incorrect with this definition, except that it is unsympathetic to those women (and their supporters) who want to terminate pregnancies.

What I do find spurious and difficult, on the other hand, is to list definitively which physical or personal characteristics (such as a nervous system or feelings) allow the right-to-life to vest. Consider: does a 1 hour old child have feelings? Or does a severely mentally retarded person? Does an individual with advanced Alzheimer’s? All do, perhaps, but in such an impaired or primitive way as to not be comparable to the rest of humanity. Therefore they should be killed. Does this statement sound incredible to you? It does to me as well, and I think that just shows the arbitrary nature of stating that one needs certain characteristics to be human.

Finally, you heap error onto error by stating that many pregnancies end with natural, spontaneous abortion, as though that impaired the humanity of fetuses which do not meet such a fate. Consider: many children die before the end of infancy or childhood. But does that impair their right to life while they still live? No. And for a person that doesn’t see any distinction between a fertilized ovum and a six year old, (in terms of the right to life) I don’t think this statement really harms the claim that fetuses are children either.

So Adam, instead of harping on what you see to be callousness, I’d like you to tell us what material characteristic a fetus possesses that entitles it to the same rights as a human being.

Not Adam, nor Eva, but will answer anyway. 

It is a human being.  Plain and simple.  Anything else is a subversion of science to ideology.  The progeny of two humans will always be a human.  We do not live in a world in which women who want babies give birth to babies, while women who don’t want them would give birth to armadillos but for abortion. 

Enough of the science, because that only tells us that, at the moment of conception, we have a living human being.

As students of history, we should realise that there are tremendous problems with classifying one group of human beings (members of the species Homo Sapiens) as “people” and another group as “not people,” “the second sex,” or the like.  The victims of abortion are not as readily seen as the victims of slavery, the Holocaust, or even of domestic violence.  They, like the elderly who are quietly euthanised where such is legal, do not cry out to protect themselves.  They do not organise marches, make ribbons, or do anything else to demonstrate that their treatment is abomindable.  Somehow, in your world, that vulnerability justifies using them as easy targets.  It’s sort of like saying that women are smaller and weaker, and are more emotional and less rational, so domestic violence is justified.  Sick, sick, sick.

In short – I have nothing but science and liberal values to offer you. 

So Adam, instead of harping on what you see to be callousness, I’d like you to tell us what material characteristic a fetus possesses that entitles it to the same rights as a human being.

Well, I’m not Adam, but I can tell you several things.
Logically, you are “begging the question” – that is you are assuming that the fetus is not a human being in your statement.  It’s reasonable to ask – if it is not a human being, then what is it?
What is the fetus? You must begin with flesh and blood.  If you don’t grant that to the fetus, then you can’t grant it to yourself, because you too are of human flesh and blood.
1. The fetus is a human being (homo sapiens) – scientifically the law of biogenesis shows that two human beings pro-create after their own kind. Pre-borns have both a mother – the pregnant woman, and a father, despite denials.
2. The human fetus has a unique flesh and blood and identity (via DNA & chromosomal patterns, including  gender).  It is not part of the woman’s body. It’s not an organ. It is a separate human being.  I could provide numerous scientific & medical references that speak to the human nature of the fetus from explanations of sperm and oocyte joining to birth. A good solid  medical embryology text would serve you well.  From an intellectually honest standpoint, you must concede that the flesh and blood is indeed a living human being, otherwise provide solid evidence to the contrary.

Your second point is – does this human being have moral agency?   Philosophically, should it be regarded as a human being when it comes to rights and responsibilities?  While scientific fact provides the flesh basis, a valid argument must be present to reject that this is not a human being with the intrinsic right to life.  Do not give me Blackmun’s Roe opinion. It’s circular logic.
Size, level of development, environment and degree of dependency are the only factors which differentiate between your pre-born self and now. Morally, these do not negate the rights of human beings, including the  foundational right to life, upon which all others hang. Throughout our legal system we have laws to stop discrimination against these factors.  Also discriminating against pre-born humans on sentience fails when the same  test is applied to other human beings.
On the moral agency factor of dependency – all rights come with moral responsibilities which cannot be rejected. The greatest is: do not murder, particularly those who are completely dependent upon us.  We do not allow murder of our newborn children.  Our responsibilities with regard to justice and to each other requires us to defend the innocent against their destruction.

Undermine that principle and brute force is the only recourse – which describes abortion perfectly. It’s also completely fallacious.

Brute force renders your initial query moot – there is no reason to ask what it is if the intention is to destroy it.

And if the fetus is an innocent human being, then no excuse justifies the killing.

can never have too many friends.

“…it seems like your argument … is solidly rooted in the idea that a potential child is the same as a child, by which logic we would conclude that an acorn is the same as an oak tree.”
“Potential child” is a misnomer.  An unfertilized egg is a potential child.  A fetus is a child as-yet unborn, who will self-develop into a child if given the sustenance intrinsically given in the mother’s womb.  By this point, no choice or deliberate act is required of the mother in order that the fetus develop into a full-term baby.
“But an acorn is not an oak tree.  And a first trimester fetus doesn’t have feelings, or the capability to survive independently (much less a functional nervous system).  What’s more, most fertilized eggs don’t become finished pregnancies.  The mother’s body aborts them if they don’t seem to be viable, or if uterine conditions aren’t favorable.
Neither do many injured or impaired adults have the capacity to feel or to survive independently.  Since sustaining these persons requires far more deliberate acts on the part of others than does pregnancy require, your line of thought suggests that leaving these persons to die is an acceptable choice if caring for them inconveniences us. You may well agree here; I’m just clarifying the fact that in searching for some “material characteristic” that evades the plain fact of conception, you have defined the right to live as contingent upon utility.
And the fact that fetuses spontaneously abort does not justify their deliberate abortion, any more than the fact that people sometimes die of starvation permits us to starve them.