1. To understand what faith in God means, we must begin with other cases of interpersonal belief. Most things we think we know are taken on faith: in scientists, in communications media, in parents, in teachers, and so on. Even in a field such as physics, most of what even experts “know” is accepted on faith from others. And virtually everything known about human history is accepted on faith in witnesses, living and dead.
2. In principle, most propositions accepted on faith could be investigated and shown to be true or not true. A physicist with enough time and resources could verify the work of other physicists. The testimony of witnesses to a past event could often be verified by examining other witnesses, reviewing the evidence, and so on. But when it is a question of a personal relationship based on faith, verification is not possible even in principle.7
For example, a young couple who meet and get to know one another exchange confidences, hopes, and declarations of affection. “I love you,” together with all that is most personally interesting and valuable in such conversation pointing toward intimacy, must be taken on faith if it is to be accepted at all. Here faith admits no verification proportionate to its certitude. What seems inconsistent with the expression of love always can be explained away; what seems in accord with it also can be accounted for even if the declaration of affection is insincere.
3. One’s faith in another is not an experience of that person. On the contrary, although expressed by words and deeds, the other’s inner self remains hidden, while everything which can be experienced is secondary to the reality one grasps in faith: the self of the other. With faith one accepts the truth of what another says about himself or herself, especially in making a commitment, and so accepts the person. In doing so, one proceeds to hope: to expect that the other will fulfill expressed intentions. And one proceeds to love: to commit oneself to communion and to carry out that commitment. Without faith there can be no intimacy.
4. The faith between a couple getting married is an especially suitable example of interpersonal faith. Their premarital faith in each other is fulfilled by the faith involved in their mutual marital commitment. Because this faith is motivated by the very marital communion it mutually accepts, it is like the living faith of a Christian. Even in the case of marriage, for those who are faithful to it, living faith cannot be falsified, because persons who refuse to judge and condemn each other always have reason to continue to believe in one another. Faith deepens as life unfolds. Communion in action constantly confirms it. Eventually the faithful couple become almost transparent to each other, yet the mystery also remains.
The mutual faith of a couple in love usually is mixed with emotion and the whole complex psychology of the romantic relationship. Most elements of such a relationship are nonessential. One can imagine a couple who have never met marrying one another by proxy, thus committing themselves to a lifelong union. The faith of each essentially bears upon the other’s expression of commitment, which includes both a proposition (that one is making a commitment) and a promise (to keep this commitment). The couple cannot make the mutual commitment without faith. If they really do make and accept the marriage vow, they have faith in one another. A similar faith is essential to all genuine interpersonal communion.
5. From the preceding, one gathers the following points about the faith required for interpersonal relationships. This faith cannot be replaced by any other sort of cognition. It concerns the person and also the propositions which he or she expresses, for the person is, in part, the self-knowledge which such propositions contain. It is the beginning of intimacy and points toward greater intimacy. Thus it always refers to the future. It leads to a common life in which each partner depends on the other to fulfill commitments; in other words, faith demands fulfillment in action. Finally, for the faithful, faith cannot be falsified.
7. Although acceptable as far as it goes, an analysis of belief which omits the irreducibility characteristic of specifically interpersonal faith is inadequate. See, for example, Bernard J. F. Lonergan, S.J., Insight: A Study of Human Understanding (New York: Philosophical Library, 1957), 703–18. Various works of Gabriel Marcel are suggestive with respect to the specific quality of interpersonal faith. See, for instance, “From Opinion to Faith,” in Creative Fidelity, trans. Robert Rosthal (New York: Farrar, Straus, 1964), 120–39. Also: Richard L. Purtill, Reason to Believe (Grand Rapids, Mich.: William B. Eerdmans, 1974), 71–79, on the nature of faith.