Okay ... Matthew really needs an editor ...

He who made us has so willed, that in mathematics indeed we should arrive at certitude by rigid demonstration, but in religious inquiry we should arrive at certitude by accumulated probabilities.

-- quoted in Michael Grant's biography of St. Peter.

Matter of degree, Cardinal. Anyway, "accumulated probabilities" is also what a historical inquiry of such figures often amounts to, as is the point of Grant's quote. The book is a bit thin (almost an extended essay on other sources), but interesting.