This is something I know, but it is also something I cannot prove.
You see, my life has been one of getting outside my boxes... only to find myself in a bigger box. Analysing my thinking before and after, I have realized that there is no amount of thinking that would get one outside the box. The "epiphany" as you have said, came from outside.
Also, the universe is a box. There are thoughts that we cannot think. But, I cannot describe them, I cannot quantify them, I cannot tell anyone else of them. There is no proof that I could ever give. Because, to do so, I would have to change the universe to include that thing/thought. And, once I did that, the universe would become bigger... and the proof would poof.