@Draug,
I don't really want to jump in here very fully, because I'm very busy this week, and I've already been through this in another thread (not the last one, but about a month ago with orathaic, Marti the Bruce, Mafialligator, et al. I don't recall the thread title off hand, sadly). Anyway, though, the problem I think is that if you're a Christian, your opinions ARE going to be based on the Bible. So if you pretend otherwise, at that point you're just being disingenuous. And honestly, if you don't have some source like that, you just have another one, equally arbitrary -- all these discussions boil down to discussions of why there is morality, and when it attaches to an organism. "Well, I think it's consciousness that's important." "No, it's self-awareness." "No, it's cognitive ability." "No, it's just life if it's the same species." How is one _supposed_ to distinguish between these? Unbelievers rarely have a well-developed foundation for their ethics in the first place, and if they do, they're as arbitrary as the above. So, I do understand what you're saying, but understand that when I have a discussion with an unbeliever and he appeals to "when consciousness begins" or something, that is every bit as arbitrary to me as my quoting Scripture would seem to him. I don't accept his choice of what undergirds morality and he doesn't accept mine.
As I argued in the other thread, I think that is what the problem is in trying to have these discussions.
_That said_, I do think that, even though people don't believe the Scriptures, they do have moral intuitions that, at their purest, do reflect correct morality, and this is why it's worth having such discussions at all -- to obliquely address your questions, dexter. Thus, for example, talking about all the various things a fetus can or does do can help somebody realize that it's human and that, according to their own moral mirror, it is wrong to kill it. I don't do that because I think that cognitive ability or a unique genome or whatever is the actual right basis for not killing it, I do it because it may call to a person's moral intuitions. Sceptics would of course all this appealing to emotions, but I don't agree -- it is appealing to moral intuitions. In a similar vein, American slavery was just wrong, but sometimes the most successful appeals were those which made slaves seem human. ("Am I not a man and a brother?").
None of this worldview dependence is avoidable. The fact -- well known since Hume at least -- is that there is NO argument from a fact, like "a fetus is conscious at X weeks," to a moral conclusion, such as "It is wrong to kill the fetus" that does _not_ have an additional moral hypothesis, such as "It is wrong to kill conscious entitites." So it is going to be necessary to go to the foundations whence people draw their moral rules, and on this, I typically have profound disagreements with pro-choicers. Not surprising, perhaps.
Among those "heuristic" arguments that I _would_ offer most, dexter, is the fact that the fetus is a potential person -- not one, like an egg, that needs to be fertilized to develop, but one that will naturally become a conscious person if not actively killed. I personally find this quite a powerful argument, though I don't find that others do. Tastes differ I guess. But the line-drawing between a fetus and, say, a sleeping adult, or on another hand, between a fetus and a month-old infant, just seem to be terribly hard once you're going to go down a path where a line needs to be drawn at all. You abhor the doctrines of Peter Singer, but as far as I can tell, all that separates you is drawing the line at a different arbitrary point on a continuum and then just denouncing his based on.... what? On moral intuitions whose consistency you don't seem to want to overprotect.
Well, that is all, sorry it turned into a bit of a ramble. I hope it was relevant to your questions. I'm now off for the rest of the day, so.... enjoy tearing me to shreds. : P