It is not some belief -- something that can be questioned, argued with, juxtaposed, compared -- it is the way of the universe. The natural order of things. That which is predestined.

Under 343, the universe itself is a living thing. And The Mantle is an extension of that truth.

It gets kinda crazy to think about.

Let's just say that those who have been called The Precursors are way, way more than some ancient alien race.

One does not have access to "the life-patterns and living wisdom of a hundred billion years" from within the confines of a universe that is supposedly 13.798±0.037 billion years old.

...like I said, it gets kinda crazy to think about. :p