The message of the Course is very consistent on this issue. The world we experience is an internal mental construct of our own making. There is no one actually out there but ourselves. "... you will begin to learn and understand ... when you met someone else, you had thought that he was someone else. And every holy encounter in which you enter fully will teach you this is not so." (OrEd.Tx.8.22) Actually there is no “out there” at all. It is all a dream, or better yet, an hallucination our mind is having. "What if you recognized this world is an hallucination? What if you really understood you made it up?" (OrEd.Tx.20.73) Let’s treat the question asked here as literal and not rhetorical. What would our experience of life be IF we understood that we made the world up? I believe then we would walk the world as Miracle Workers like Jesus did, and this is exactly what ACIM is calling us to do.