I bet a lot of people when they think about the soul imagine something nebulous—a kind of glow, or gas, or force-field, or the like—permeating the body. Certainly, this is how I imagine it. It's funny that nobody imagines the soul to be like a rock. Yet, aren't both images just as much off? The nebulous something—that fails convey the stability and unity of the soul. And the rock—that fails to convey immateriality.
(I am not about to urge that one not imagine anything when thinking about the soul. When I think about mathematical entities, I do imagine physical objects—for instance, graphs—that represent them. But that only rarely leads me astray—much more often, it helps.)