IT is acknowledged in the church that everything good comes from God and nothing of it from us, and therefore that we should never take personal credit for anything good. It is also recognized that evil comes from the devil. This is why people who talk from the doctrine of the church describe people who are acting well and who are talking devoutly and preaching as being led by God, and say the opposite about people who are acting maliciously and speaking blasphemously. None of this could happen unless we had a union with heaven and a union with hell, and unless those unions were with our volition and our understanding, since it is from these that the body acts and the mouth speaks. We need now to describe what this union is like.
There are good spirits and evil spirits with every individual. We have our union with heaven through the good spirits and our union with hell through the evil ones. These spirits are in the world of spirits, which is intermediate between heaven and hell and will be specifically treated later. When these spirits come to us, they come into our whole memory and from there into all our thinking—evil spirits into the matters of memory and thought that are evil, and good spirits into the matters of memory and thought that are good. These spirits are totally unaware that they are with us. Rather, as long as they are, they believe that all these matters of our memory and thought are actually theirs. They do not see us, either, because their sight does not extend to things in our subsolar world.
The Lord takes the greatest care to prevent spirits from knowing whom they are with. If they did know, they would talk with them, and then the evil spirits would destroy them; for evil spirits, being united to hell, want nothing more than to destroy us not only as to spirit (that is, as to our love and faith) but as to our bodies as well. It is different when they do not talk with us. Then they do not know that we are the source of what they are thinking—and what they are saying to each other, since they talk to each other just the way we do—but believe that these matters are their own. They value and love whatever is their own, so these spirits are constrained to love and value us, even though they do not know it.
This kind of union has become so familiar to me through years of constant experience as to be commonplace.
from Heaven and Hell, Sections 291, 292