Langdon could scarcely believe his own supposition, and yet, considering who had given this stone cylinder to them, how he had given it to them, and now, the inlaid Rose on the container, Langdon could formulate only one conclusion.
There are no more uses of "supposition" in the book.
Show samples from other sources
It is a foolish supposition.
She paints a vivid picture, but we must remember it is all mere supposition.