What is real? This has been a question of mine for a long time. From a physics perspective Brian Greene explores the question in his new book The Hidden Reality, Parallel Universes and the Deep Laws of Cosmos. While he's a physics professor at Colombia University, he writes in layman's language as far as such esoteric concepts can be expressed outside of mathematics. It took me two months to read the book – not a page turner but a thought provoker. I recommend reading the last chapter first to get an over view of the nine Multiverses Greene systematically explains in the the book. Basically, the idea is that there is more than one universe, but there isn't agreement about how many and how they manifest. Of nine Multiverses that may be possible, the one that blew me away is the possibility our world could be someone else's computer simulation. Shades of the move the Matrix. In the beginning of the chapter on” Black Holes and Holograms – The Holographic Multiverse,” Greene refers to Plato's allegory of the cave – that we are people chained facing the back wall of a cave watching shadows of the real world. That our perceptions are but a faint inkling of a far richer reality that flickers beyond reach. (Gurdjieff would say that we can awaken to this far richer reality.) Greene has written two other excellent books – The Fabric of the Cosmos and The Elegant Universe. Take a stab at them. I already have Fabric of the Cosmos and am going to buy The Hidden Reality since I read the library copy and couldn't scribble, underline and make notes.