"The chief difficulty is that God demands of us that we live by faith: faith in God, God's sovereignty over the future, God's sufficiency for the present; while, on the other hand, the various other gods whom we can serve appeal to us in terms of the things which we can see and the forces which we can calculate. The choice between the life of faith and the life of sight is a choice between a God whom only faith can apprehend and gods whom one has only to see to understand."