In reference to my last post, when I tried out on Sarah the assertion that the proposition 'Humans [and only humans] have souls' is a proposition about biology, I was met with complete disagreement. Presumably she would describe it as a proposition about the supernatural. That's to say, it's a claim that, though we're biologically one of the set of animals, in some sense supernaturally we're outside that set.
I have real difficulties with this, and the reasons are obvious - or they are to me. There are things that flow from the claim that humans have souls, and these are not insignificant things, with not insignificant moral implications, not to mention implications with respect to our relationship to other animals. As Jason Rosenhouse puts it:
If you hold views about a supernatural realm that have absolutely no empirical consequences whatsoever then you have nothing to fear from science. There are even certain religious systems that posit such a realm. But that is not the sort of faith held by most Christians.I'm not even sure that any religious system posits a supernatural realm with no consequences [we say 'empirical consequences' but we know of no other] in the natural realm. Those who believe in ancestor spirits rarely if ever believe that they have no effect on this world - that is the point of the belief. The spirits account for events otherwise inexplicable in this world.
We can, I suppose, believe in something supernatural with no effect on this world, but it requires some effort. For example, one might believe in reincarnation, but a reincarnation process which is arbitrary, bearing no relation to rewards and punishments. In other words, in our next life we might be a rodent, a bacterium, or a rich, beautiful, popular human being, regardless of how we behave in this life. This of course, would render us the playthings of whatever forces decide upon these things, and there would be no moral dimension to such a belief. Or would there? If we firmly believed in this form of reincarnation, might we not want to opt out as soon as life in this particular incarnation turned ugly? If the going gets rough, why not top yourself? Your next life couldn't be much worse, and might be a whole lot better. And if you're safe in the knowledge that you'll continue to live, you'll be like a gambler, throwing in your lot time after time for the next world, until you come up with a win. Though of course, you'll only be able to gamble when you return as a being with a higher consciousness - bacteria and mosquitoes don't have the wherewithal to gamble. Such a belief, firmly held, might make suicide terrorism more attractive, not to mention murder. You can escape the consequences of your actions into a new world of possibilities.
This is just one example of how difficult if not impossible it is to imagine a supernatural belief having no effect on our behaviour in this world - the world science deals with. Sarah suggested that believing that you have an extra, invisible finger would be an example of a belief that is clearly not biological. In other words, the believer might accept that the finger has no 'biological' existence but claim that it nevertheless exists. Again [and the comparison with gods here is obvious] if the invisible finger merely exists, and makes nothing happen in the natural world, this wouldn't be a problem, though one might wonder about the point of such a belief. If the believer claims that the finger is actually used to pick things up and so forth, it would be reasonable to ask for evidence of this. If the finger's purpose is to, say, point to wrong-doers, then, if it is invisible, nobody sees it and it wouldn't make any difference. If only the owner of the finger sees it, or claims to see it, that's a serious claim that needs to be investigated - it hardly matters whether you call it a biological claim or a moral claim - it's a claim that the person [or his invisible finger] knows something about this world. It needs to backed up.
So, returning to claims about the exclusively human soul, about humans being in the image of god, and of having somehow inherited 'original sin' or being somehow 'fallen' - it really doesn't matter so much whether you call them biological claims [though that's how I would prefer to classify them]. What needs to be emphasised is that such claims have this-worldly implications. They seek to tell us something [in fact, a lot] about what we really are. In doing so, they compete with modern biology and modern psychology, the primary aims of which, when they are dealing with homo sapiens, is to give us an account of what we really are. The accounts are very different, and quite incompatible.