Faith is not a weak form of belief or knowledge; it is not faith in this or that; faith is the conviction about the not yet proven, the knowledge of the real possibility, the awareness of pregnancy. Faith is rational when it refers to the knowledge of the real yet unborn; it is based on the faculty of knowledge and comprehension, which penetrates the surface and sees the kernel. Faith, like hope, is not prediction of the future; it is the vision of the present in a state of pregnancy.
The statement that faith is certainty needs a qualification. It is certainty about the reality of the possibility – but it is not certainty in the sense of unquestionable predictability. The child may be stillborn prematurely; it may die in the act of birth; it may die in the first two weeks of life. That is the paradox of faith: it is the certainty of the uncertain. It is certainty in terms of man’s vision and comprehension; it is not certainty in terms of the final outcome of reality. We need no faith in that which is scientifically predictable, nor can there be faith in that which is impossible. Faith is based on our experience of living, of transforming ourselves. Faith that others can change is the outcome of the experience that I can change.
There is an important distinction between rational and irrational faith. While rational faith is the result of one’s own inner activeness in thought or feeling, irrational faith is submission to something given, which one accepts as true regardless of whether it is or not. The essential element of all irrational faith is its passive character, be its object an idol, a leader, or an ideology. Even the scientist needs to be free from irrational faith in traditional ideas in order to have rational faith in the power of his creative thought. Once his discovery is “proved,” he needs no more faith, except in the next step he is contemplating. In the sphere of human relations, “having faith” in another person means to be certain of his core – that is, of the reliability and unchangeability of his fundamental attitudes. In the same sense we can have faith in ourselves – not in the constancy of our opinions but in our basic orientation to life, the matrix of our character structure. Such faith is conditioned by the experience of self, by our capacity to say “I” legitimately, by the sense of our identity.
Hope is the mood that accompanies faith. Faith could not be sustained without the mood of hope. Hope can have no base except in faith.
excerpt from: Erich Fromm (1968) The Revolution of Hope.pdf : Faith