When you understand it properly, the doctrine of vocation--"doing everything for God's glory"--is not a platitude or an outdated notion. This principle that we vaguely apply to our lives and our work is actually the key to Christian ethics, to influencing our culture for Christ, and to infusing our ordinary, everyday lives with the presence of God. For when we realize that the "mundane" activities that consume most of our time are "God's hiding places,"...