In the book "When Einstein Walked with Gödel" by Jim Holt, It seems like that assumption is not as clear as it seems. I am not able to articulate it well enoug

In the book "When Einstein Walked with Gödel" by Jim Holt, It seems like that assumption is not as clear as it seems. I am not able to articulate it well enough and I don't have the book at hand. If my recall is accurate then there is a bit of a question if there exists a "final number".