In both of his major works, Insight and Method in Theology, Bernard Lonergan included extensive discussions of the role of believing in our lives, believing, that is, not first of all in a religious sense, but in the ordinary sense that believing vastly expands beyond our own experience, inner or outer, the realm of what we take to be true. He used to say, “Ninety-nine percent of what a genius ‘knows,’ he believes”–of what a genius knows, never mind the rest of us. It is probably impossible for us to separate out what we have come to think true on the basis of our own experience, our own understandings, our own judgments from what we have learned and think true because of what others have communicated to us about their experience, their insights, their verifications. Even scientists believe most of what they know, and think it quite reasonable to do so: they don’t feel it necessary to repeat the experiments that led to the state of scientific knowledge when they begin their work much less the ones reported to them as having been successful today. Here is Augustine’s list of things we know only because we believe others:

Because there are two kinds of things that are known, one that of things that the mind perceives through a bodily sense, the other of things the mind perceives by itself, some philosophers chattered on in opposition to the senses. Now they could hardly doubt that minds of themselves have certain very strong perceptions of true things, such as, “I know that I am alive.” But far be it from us to doubt that we learn true things by the bodily senses. Through them, after all, we learned about heaven and earth and the things known to be in them to the degree that he who created both us and them wished us to come to know. And far be it also to deny that we know things that we learn from the witness of other people. Otherwise we wouldn’t know that there is an ocean; we wouldn’t know that there are lands and cities that are commended to us by their great renown; we wouldn’t know that there were people and their works that we learned by reading works of history; we wouldn’t know the things told to us every day and confirmed by constant and consistent indications; finally, we wouldn’t know where and from whom we were born, because we believe all these things on the testimony of others. (De Trinitate, XV, iv, 21; PL 42, 1075)