Recently, I've been reading Hidden Realities by Brian Greene which explains the physical rules allowing multiple universes while trying to simplify the math. It's a very interesting book, but also bring up many knowledge issues. The largest I noticed was this. There is a principle called the Anthological Principle. THe basis of this is that any astrophysical discovery we make must move us more and more toward averageness. Basically, we should and cannot be unique. The knowledge issue this brought up is Why must scientific discoveries prove humanity is average and not unique?
The book itself discusses how, most likely, we can never truly prove that multiverses exist, just that they are very likely or unlikely.
Finally, I'm currently reading about less is more in physics. If given the location of every atom, scientists do not know what it makes up. However, give him the basic shape of a lion, and the scientist knows its a lion. This brings up, "Is there a limit to the amount of information Humanity should attempt to unearth?"
Later, it is going to talk about artificial universes, but I'm not there yet. I'm just starting holographic universes.