The zygote (or successive stages before “fetushood” is reached) are not yet sentient, no doubt. But as I argued in my original post, sentience is a rather subjective and ethereal concept in itself. The zygote, blastocyst, etc. are, however, stages in the development of a human being.

I would argue that there is no ethereal concept of sentience when there is no central nervous system. For me, that’s good enough to differentiate between a cluster of cells with a potential of being human and a human.

Differences in viewpoint like this are going to be the major stumbling block that will keep this debate heated for the next 100 years. Once we can clone people from a single cell – any cell – the waters are going to be further muddied. I recommend Blade Runner as a layman’s introduction for that mess to come. (Personally, I think Deckard was a Replicant as well…)

I grant the point that sometimes a zygote can split and it may end up being MORE than one human being. I’m not sure that helps your argument any. At any rate, at minimum, we can say that the zygote MAY be or is LIKELY to be a unique human being, and that alone would protect it from harm – for the same reason that we can’t shoot at some rustling bush in the woods if there is any doubt that it might be a human being behind that bush.

As for your exciting example of a meteorite hitting great gramps, that would not have killed me. It would have had the effect of preventing me from ever existing, yes, but that’s a different thing entirely.

The zygote (or successive stages before “fetushood” is reached) are not yet sentient, no doubt. But as I argued in my original post, sentience is a rather subjective and ethereal concept in itself. The zygote, blastocyst, etc. are, however, stages in the development of a human being.

Your final question – what is the property of a small cluster of cells that makes it a human? If it is not the spiritual concept of the soul, what is it?

Basically the same as what I said above. Simply that it is genetically human in an early stage of development, which simply needs shelter and nutrition to grow into progressive stages. This would separate it from, say, a chicken which is in an early stage of development but which is not genetically human. It would also separate it from some scraped skin cells which are genetically human cells, but not, as an entity, a stage of development of some human being.

You can delete the previous two posts, which expose me as an XHTML idiot and a poor typist respectively.

However, the Church does make the biologically correct statement that at the moment of conception, an individual, unique human being comes into existence.

This is not a biologically correct statement. At the moment of conception, a zygote comes into existence. It’s not even close to being a fetus yet. A zygote can do many things, including splitting in two or more and making twins, triplets, etc. So, making the claim that the moment of conception an unique human being comes into existence is disingenuous even at face value. It has the potential to be a handful of people.

A zygote is a single cell with mixed DNA from two individuals. That’s it. A fetus is much more. This is where the debate falls: when is this biological mass a human? Biologically speaking, I don’t know that we’re ever going to decide on a clear cut line when fetal development is involved, but a single cell, or a cluster of cells with no human attributes other than a chemical strand of genes? That’s just a mass of cells. There isn’t even any defined differential cell structure for some time. I can scrape skin cells off of my arm which are just as genetically human as any zygote, but we don’t call that a human being.

The fact is, from conception to birth to our shriveled up final doom, they are all various stages in human development. If my mother aborted me in 1964, she would have killed “me” as surely as if someone shot me in a psycho rampage today.

This is unfortunately a straw-man argument. If a 2,000 lbs. meteorite struck your great grandfather before he met your great grandmother, you would have been “killed” in the same argumentative manner.

Killing a potential is not the same as killing an existent sentient life. A small clump of cells is not a human – it is a potential to be a human. A fetus, with a central nervous system…I’d say that’s human, but others are going to debate that point.

From zygote, up to but not including fetal development, in order to view this tiny, unformed mass of cells as anything more than just a mass of cells; you have to attribute some non-empirical properties to that mass.

So, since you currently represent the only Catholic viewpoint here (and probably the only Christian one), what is the property of a small cluster of cells that makes it a human? If it is not the spiritual concept of the soul, what is it?

You should actually read the writings of responsible Christians. Prohibitions of porn and masturbation have no corellation with an alleged desire to raise more Christians.

In general terms, Catholics are encouraged to be generous in their family size, yes, but not beyond what is responsible for that particular family. The reason to encourage generosity is that a new person is a good, indeed an immortal good.

I can understand your cynicism, but it’s off base.

Everyone tries to spread their beliefs – you shouldn’t fault Christians or other religious believers for doing so, as long as their weapons of choice are persuasion and prayer, rather than, let’s say, the scimitar.

As for the article you linked, I think it was intended to convince Catholics that they are bound to believe that the human soul is infused at conception, and not as a general argument against abortion per se. I am not at all convinced that he is correct in his reasoning there. The Church has never attempted to fix the point at which a soul is infused.

However, the Church does make the biologically correct statement that at the moment of conception, an individual, unique human being comes into existence. This human being may not be intentionally killed, regardless of arguments about the timing of the human soul.

Even an atheist could agree (and some do) that the killing of a biological human being should not be allowed, never mind any arguments about the soul, which an agnostic may not need to concern themselves with.

The alternative is some variant of the “stage of mental development” criteria, which is all very subjective and which no two people really seem to agree upon. After all, if a 1 month old or even 1 year old baby is not allowed to be killed, then based on this criteria, surely there are many animals whose rights should be protected by law.

The fact is, from conception to birth to our shriveled up final doom, they are all various stages in human development. If my mother aborted me in 1964, she would have killed “me” as surely as if someone shot me in a psycho rampage today.

So, no intangible bullshit from me today, O. I do agree that Christians should not construct arguments against abortion based on the human soul. It is not necessary and indeed counterproductive.