I've spent a great deal of time pondering this and related topics. I've spent time investigating various philosophies and religions for clues. Those clues combined with the effects of various psychedelic substances have led me to highly doubt the proposed concrete nature of an external universe that we are raised to believe. One thing philosophy has taught me is that any time someone purports their ideas and theories to be the truth, there is a high probability that they are wrong. (If you examine their premise, they often state something like, "Because of X then Y. All you need to ask is, "What about Z and H and 7 and green, etc...?) My experience has led me to believe that this world is a false facade created by our minds to shroud the unspeakable horror that lies beneath. Our type of consciousness would not survive were it not for some type of delusion. I believe in the observer created universe, but it's a tricky. A bootstrap theory if you will. In a more practical sense here's an example. There are many TV channels. Do you watch all of them? No. You watch the ones that most closely align with whatever is already inside of you. The same can be said for books. You don't read a book about something you know nothing about, that is unless you want to know about it. On more than one occasion I have read a book where it feels like the words are spilling out of my mind and on to the page. I've had similar experiences with music videos and movies.