the Dark-Suck theory of light

One of my Teachers were messing around one day and he told us about a theory that he proposed in college for fun. His premise for this theory was that devices and things that put out light didn't do that at all. Instead, for example, a lightbulb would suck the darkness out of a room, and in it's place would be light. Light bulbs, according to the theory, would be dark sucking or countering devices. The intensity of the light would depend on how much darkness is taken from the room.

Light bulbs are taken for granted too often. When you enter a darken room, you flip the light switch. What happens? Does a light come on or does the darkness leave? Don't think about it too hard.