As far as I have been able to tell, we do live in such a world: reality is a dream, and the only truly concrete fact is subjective awareness. OP asks, "How wou

As far as I have been able to tell, we do live in such a world: reality is a dream, and the only truly concrete fact is subjective awareness. OP asks, "How would someone know they lived in such a world?" Well if you study and practice, like, at all, you find that "magical thinking" of what some call "co-creation" happens. If you keep going like that, you find that reality is fluid, up to the point where you can materialize or de-materialize physical objects including your own body. The time delay between imagining something and having it exist in the "real" world reduces. (This is the resolution of the riddle "Make the inside like the outside and the outside like the inside.") At that point, if you have your head on straight, you start to wonder who is really doing all this? Is it "I"? From there you begin to realize that your own "I" is an illusion and there is only one "I", the I of the Universe. So that's the way "out".