I think one can distinguish a soul culturally, and have it mean something, but it's not a transcendental truth.*
*To put an easier way, the soul is indistinguishable enough from bodily functions to make the body/soul division, on which the definition of soul rests, obsolete.
Ok, I think I understood what you said better before the footnote. I thought you were saying that what we define as a "soul" is a subjective thing that differs from person to person, and even more widely from culture to culture, so there isn't a universal truth behind the concept. But your footnote confused me and made me not sure that's what you meant anymore...
I did muddle that a bit, I blame it on the cold I was getting off of. They aren't the same thing, are they?
By the first, I did mean that the soul is something defined subjectively, and it changes from individual to individual and religious tradition to religious tradition. By the footnote, I meant something else entirely. (Why did I tie the two together?) It was my opinion, that the soul and body binary doesn't work because the distinction between the two is too vague in our modern, scientific understanding of the mind.
There are a few things which crop up when you get deeper into discussion, though. One thing I find most enlightening is that last item on the relationship between sentience and a soul. So, is sentience a necessary and sufficient condition for a soul (i.e., does everything with self-awareness have a soul), or is sentience a necessary but not a sufficient condition for a soul (i.e., is it possible for something to be self-aware but still be soulless)?
There are some that would say that a sentient robot is still soulless, for any variety of reasons. It could be because it's not organic, because it was seemingly not created by God, because it has no intrinsic impulse towards morality, or what have you. I can't find a good argument in that direction though, so I'm more inclined to believe that sentience implies a soul.
However, I would argue for animals on two points. One, that animals also have a form of sentience, the only distinction being that theirs is not communicable as ours is (I speak, therefore you hope I think). Two, that if they don't have full sentience, they might nevertheless have a soul. (That would tweak your "necessary and sufficient" considerably.) But I'll leave that for now, if anyone is interested in the argument, because it's nearly 1 AM and I need sleep.