We may define “faith” as a firm belief in something for which there is no evidence. Where there is evidence, no one speaks of “faith”. We do not speak of faith that two and two are four or that the earth is round. We only speak of faith when we wish to substitute emotion for evidence. The substitution of emotion for evidence is apt to lead to strife, since different groups substitute different emotions.
Source:Part II. The Conflict of Passions, Chapter 7. Will Religious Faith Cure Our Troubles?