"He who made us has so willed that in mathematics indeed we should arrive at certitude by rigid demonstration, but in religious enquiry we should arrive at certitude by accumulated probabilities." This quote by Cardinal Henry Newman appears in the first chapter of Michael Grant's Saint Peter (page 3). Michel Grant is stating his case that we know very little about the historical figure of Peter but that there are enough "probabilities" that "exist in abundance" that he feels it is possible to know what saint Peter was like.
Cardinal Newman, of course, did not have Saint Peter in mind when he spoke about certitude. He was talking about religion in general. It seems to me that, his quote also applies to Christianity (he was a Cardinal after all) and is useful today when we confront the postmodern conundrum that some people encounter when they try to reconcile Christianity in the same way that they prove the accuracy of mathmatical equations or reconcile scientific questions. That process of inquiry simply does not work for or apply to religious belief. Prior to the age of science this was not a problem for those immersed in Christianity for they had a different way of "knowing". Their "certitude" (belief) was the result of their own experiences, of listening to or of studying wise individuals who came before them, of reading scripture and through prayer. This way of "knowing" needs to be adopted by people today. Indeed, many who express and live their faith do "know" through this process. To come to understand in this way we have to have our eyes, minds, and hearts open to accumulate these probabilities and, because we cling so strongly to the process of scientific inquiry, this is difficult for post modern people.
Michel Grant was of course talking about knowing a man, Saint Peter, and an accurate picture of him can be developed. Cardinal Newman was, however, speaking about God and to fully know God who is infinite is impossible for finite humanity. There is, however, a BIG but here; because we can know what God was like in human form through the person of Jesus and this is where our "certitude" can rest.