The Subtle Body Has a Location
It is the subtle body, not the spirit, that makes the difference between a living person and a corpse. Your spirit doesn’t have to be in your physical body or anywhere near it for you to remain alive. In fact, it’s nonsensical to talk about where a spirit is, since spirits don’t have any location in space. For the spirit to “go away” simply means for it to turn its attention elsewhere, as it often does when you are sleeping. The subtle body, though, has a location. It has to stay with your physical body as long as you are alive. Ghosts are the detached subtle bodies of those who have died. If you have ever felt the presence of a ghost, you could probably say pretty clearly where it was, and approximately how big it was. By contrast, a meeting with a spirit feels more like it’s happening in your mind. When a loved one dies, you might experience them for a while as a ghost. Then the subtle body goes away, and should you meet them again, what you will encounter will be their spirit.
— On Becoming an Alchemist, p. 46