God of the Gaps arguments are a discredited and outmoded approach to apologetics, in which a gap in scientific knowledge is used as evidence for the existence of God. Before the scientific revolution of the last four centuries, such arguments were commonplace and widely accepted, presumably because the "gaps" were large and showing no signs of shrinking. A lightning bolt crashes down, the peasants working in the field cross themselves and say "well, we don't understand that, so it must be God."