The ancient Chinese believed we had two souls. The Hun 魂, the spiritual soul, would leave behind the body at death and become one with Heaven. It's your idea, your legacy, your aura, your personhood. The Po 魄, the Earthly soul, would linger with your body, slowly dissipating as your corpse decays and returns to the Earth. It is your sense-consciousness, physical awareness, and material instincts.

Corollary to this is that if your body never decays, your soul will never truly be able to pass on from this world. This is why the Norse burned the dead and their belongings, to hurry their passage from this world to the next, it's why an old Victorian house can be "haunted," and it's why the Catholics keep old saint's skulls around to show off.

Variations of this idea were extremely common and widespread in the ancient world, probably originating in Siberian shamanism and its various Pagan descendants. The Egyptian's Ba and Ka, the Norse's Hamr and Hugr. Even the Hebraic Neshama, Ruach, and Nephesh, but it was the Chinese who were the most theologically explicit with it. Heaven and Earth in Chinese religion, or more universally "the spirit world" and "world of the dead" is one of the few theological ideas that is present in all ancient religions.

Heaven is essentially the spiritual-mental realm; it's symbolism and idea and meaning and thought. Think Plato's hyperuranion (literally beyond-Heaven,) whose philosophy was to one extent or another, an explication on the Indo European idea of Heaven.

Earth, on the other hand is the purely material realm, associated with animals and nature in general. It is the literal physical reality of existence that we inhabit, it is our senses and desires, fear and joy, pleasure and pain, and will. The Buddhists called it Naraka, the Underworld, and treated it not just of the realm of matter, but also the state of mind where one is trapped in a cycle of suffering by their own Earthly desires. Hell is not a place, it's a mindset.

And reality as we experience it is the overlay of these two realms. The Buddhist Middle-Realm, the Norse Midgard, the early Daoist's "Realm betwixt Heaven and Earth, 天地之間." Without Heaven, Earth is the mere fact of matter, a meaningless biological machine realm of determinism and pure animal instinct. Without Hell, Heaven is an unchanging purposeless crystalline idea, endless ceaseless stasis without pain or conflict, and so without pleasure and love. And in between and together is our lives, our middle realm, beneath the sky and above the soil; where we love and live according to our own freedom, before we die and return to the great mystery from which we were born.