D&D's soul? How are we supposed to answer if we are materialists?
This is an interesting point, because some think that D&D's intrinsic qualities and unique characteristics are a function of its mechanics (flesh and blood) and thus the "soul" is either a non-entity or purely subjective and thus difficult to characterize in any kind of universal way.
Let's take a look at this word "soul," however, because I don't think its usage requires a belief in anything supernatural or outside of a materialist perspective (except for, perhaps, the most diehard materialist).
To quote Sufi mystic Hazrat Inayat Khan,
The body is the visible part of the soul, and the soul is the invisible part of the body.
Another way to put that is that not only are the two--body and soul--part of the same "thing" or entity or being, but rightly understood, the body is how the person feels on the outside, how it can be perceived and weighed and measured in the physical, sensible domain, whereas the soul is how the person feels on the inside, subjectively. Thus it isn't inherently "wrong" in terms of materialism to say "I have a soul" or "I am a soul" if you are simply referring to your subjective, inner experience. That is not a supernatural or spiritual statement, necessarily; it could simply be a subjective statement of one's own inner experience of self.
To put it yet another way, the brain is how the mind looks from the outside, whereas the mind is how the brain feels/is experienced from within. Whether or not the mind/soul exists beyond the brain/body is a metaphysical question that stretches us beyond the scope of this conversation.
In terms of D&D, I would say that if we're talking about its "soul" then we're talking about an inner experience, not the parts that make it up. I don't think it is a stretch to say that the inner experience of self is more defining and primary to who one is than any "outer part." For instance, I have a body, I have arms and legs and fingers and toes, but I am not any of those parts. I am I. Now if I lost any of those parts, certainly my experience of self would change, but I would still remain I. My sense of being and self is not lost because a part of my body is lost.
What I'm getting at is that the experience of D&D is not primarily in the parts, but in the inner experience. So I think Frostmarrow's perspective is right on point:
To me D&D's soul is a pastime rather than a product. It's something to tinker with, think about and play with you friends. It's an engine for creativity. The soul of D&D is not the contents of a box. It's what you can make with that content and your imagination.
TSR put it succinctly: "Products of your imagination."
Thus the "body" of D&D is the rules, the books and boxes, miniatures and maps, the systems and sub-systems; the "soul" is the inner experience of imagination. The body forms a structured context for the soul experience, channels if you will, through which the "soul waters" may flow, although it doesn't inherently limit it.
