In John’s gospel, Jesus declares himself to be “the light of the world.” Indeed, throughout that gospel, John seems to play with images of darkness and light: Jesus was “the light of all mankind,” for example, while Judas went out into the night to do his dirty work. And one of the most striking claims of 1 John comes only five verses into the letter. “God is light,” he declares, a statement that carries with it a moral imperative: if you believe in and serve a God who is light, then you must not walk in darkness.