Belief, like fear or love, is a force to be understood as we understand the theory of relativity and principles of uncertainty—phenomena that determine the course of our lives. Yesterday, my life was headed in one direction. Today, it is headed in another. Yesterday, I believed I would never have done what I did today. These forces that often remake time and space—that can shape and alter who we imagine ourself to be—begin long before we are born and continue after we perish. Our lives and our choices, like quantum trajectories, are understood moment to moment, but each point of intersection, each encounter, suggests a new potential direction.