There’s a saying that I’m sure you’ve come across on occasion: “You don’t have a soul. You are a soul. You have a body.” It’s often misattributed to C.S. Lewis, but I don’t think he ever actually said anything of the kind. It shows up several times before Lewis, usually in wording pretty close to that, but we don’t know for sure how it started. The idea it reflects it pretty similar to the Gnostic belief that the material world is an illusion meant to hold us back. While it was rejected by orthodox Christianity, it kind of seems like it managed to sneak back in. References in the New Testament suggest a bodily resurrection, as also mentioned in the book of Daniel, apparently a favorite of Jesus. When this general resurrection didn’t happen, it became more common to think of souls as going to Heaven or Hell after death. Some Christian denominations still hold that the bodily resurrection will eventually occur, while others largely disregard it. The thing is, if the soul can live on eternally without the body, it kind of makes life on Earth somewhat irrelevant. Sure, the mainstream belief differs from the Gnostic in that it affirms the reality of material things, but a human lifespan is apparently a drop in the bucket compared to how long a soul can exist.
I must admit to being curious as to what exactly people think a soul is, and how the concept developed. It’s the animating force of the body, but at the same time it also seems to encompass a person’s mind and identity. As such, it’s still YOU moving on into the afterlife, not just a collection of spiritual energy.
I can’t say I’m sold (souled?) on the idea myself, as it seems to me that the prevailing wisdom is that identity is stored in the brain and can’t be separated from it. I think the idea that personalities can simply cease to exist is inherently disturbing, however, so different cultures came up with different ways they could live on. I’m not saying it isn’t a tempting idea, just that I find it unlikely. While there are still debates now as to whether, say, animals have souls, some of the oldest known religious beliefs are animist ones in which even non-living things do.
Of course, back then no one knew about cells, so there wasn’t as much of a line of demarcation between life and non-life. Also, I’m not sure whether animists believed that souls could be separated from bodies, so the implication isn’t necessarily that a rock can have an eternal afterlife.
The Wikipedia article on ghosts suggests that the soul was commonly associated with breath, since living things stop breathing when they die. That could be why ghosts are often thought of as wispy, like frozen breath on a cold day.
It also appears to be a pretty old belief that the dead still look like they did in life. This would probably be essential if you’re going to recognize the spirit of someone you knew, unless that information is just automatically filtered into your mind or something. While it’s tempting to think of a soul as pure energy, I don’t think that really fits with the common understanding. Ghosts can float around and walk through walls, but they’re also frequently regarded as interacting with physical objects.
In reading about mythology, I’ve come across many different concepts of the afterlife and the world of the dead. The Greek Asphodel and the Hebrew Sheol are more or less shadowy underground realms of eternal boredom. I think a lot of people would rather just cease to exist than go there, but I guess at least you can still occasionally keep in touch with your living friends and relatives, like when Odysseus chatted with the shades.
There are also many variations on souls being rewarded or punished for their deeds on Earth, and often in ways that suggest they still have some physical substance. After all, if you no longer have a body, you would think you wouldn’t need to eat and couldn’t feel pain, but the honored souls were still said to spend their time feasting and the damned burning in fire.
Tantalus‘ punishment in Tartarus consisted of being denied food. Some cultures that practice ancestor worship will offer food to their late predecessors, and it seems that ancient Egyptians thought they could bring some things with them to the afterlife. Some old Egyptian and Mesopotamian beliefs held that the next life wouldn’t be a place of eternal reward, punishment, or boredom; but rather another life much like on Earth. It seems common now to regard these very physical descriptions of the afterlife as merely symbolic, and maybe they were always intended to be. There’s really no way to tell until someone makes a trip there and back, and I don’t mean that Heaven Is for Real kid. Indeed, people who claim they’ve seen Heaven or Hell often have ideas suspiciously close to the popular conceptions that they’ve almost certainly learned about before.