A great deal of experience has taught me that we are spirits inwardly, experience that would fill whole volumes, as they say, if I were to include it all. I have talked with spirits as a spirit and I have talked with them as a person in a body. When I have talked with them as a spirit, they could not tell that I was not a spirit myself, in just as human a form as theirs. That is how my inner nature looked to them, because when I talked with them as a spirit, they could not see my material body.
We may gather that inwardly we are spirits from the fact that after we depart from our bodies, which happens when we die, we are still alive and just as human as ever. To convince me of this, [the Lord] has allowed me to talk with almost all the people I had ever met during their physical lives, with some for a few hours, with some for weeks and months, and with some for years. This was primarily so that I could be convinced and could bear witness.
I may add here that even while we are living in our bodies, each one of us is in a community with spirits as to our own spirits even though we are unaware of it. Good people are in angelic communities by means of [their spirits] and evil people are in hellish communities. Further, we come into those same communities when we die. People who are coming into the company of spirits after death are often told and shown this.
Actually, we are not visible as spirits in our [spiritual] communities while we are living in the world because we are thinking on the natural level. However, if our thinking is withdrawn from the body we are sometimes visible in our communities because we are then in the spirit. When we are visible, it is easy to tell us from the spirits who live there because we walk along deep in thought, silent, without looking at others, as though we did not see them; and the moment any spirit addresses us, we disappear.
from Heaven and Hell, Sections 436-438