Esoteric Lesson
After death, and even during sleep, we must lay aside our thoughts, with the exception of those produced by spiritual science. But our feelings and impulses of will extend into the supersensible realm, and impressions can therefore be made on them. This happens, for example, when we see our double. But it can also be that someone sees their double, not because the angelic being shows it to them, but because, even if only for a moment, their etheric body has become free and they now see their physical body in front of them. And it is also possible that one sees one's double simply because one has upset one's stomach and the etheric body—perhaps only in those parts that supply the stomach—has become free for a moment. All of this must therefore be carefully distinguished from one another.
Cite:
GA 266c/1913-04-11/p008 · edition English