Once he accepted the axiom--and he was no longer prepared to doubt it here--he could follow the book far better than he'd been able to follow his own course in semantics.
He could follow the book because it was very simple to read.
mnli hypothesis: He could follow the book because it was very simple to read. premise: Once he accepted the axiom--and he was no longer prepared to doubt it here--he could follow the book far better than he'd been able to follow his own course in semantics.