When it comes to black holes, even though we can’t say what their constituents actually are— since we don’t know what happens when matter is crushed at the black hole’s center—we can say confidently that rearranging these constituents will no more affect a black hole’s mass, charge, or spin than rearranging the pages in War and Peace will affect the weight of the book. And since mass, charge, and spin fully determine the face that a black hole shows the external world, all such manipulations go unnoticed and we can say a black hole has maximal entropy.
