What does it mean to live by faith? Answers are more elusive than ever. Beginning with a rich discussion of the Reformation legacy, historian-theologian B.A. Gerrish responds that if we release our thinking from sectarian, partisan lenses, we find that faith denotes a multitude of impulses-trust, doubt, fidelity, and confidence-and is a fundamental human posture. It undergirds not only "saving" faith but also "secular" varieties in other religious...