In a mostly dark room, where only pale light and shadows are discernible, even the most benign objects take on frightening shapes. The bedpost might look like a witch. The curtains, as they rustle in the breeze of the open window, might appear to be ghosts. An overstuffed chair in the corner might appear to be a monster with his arms outstretched, waiting to grab you. But if you were to simply turn on the lights, the room would suddenly be cozy and warm and inviting. Your imagination is going crazy over an upcoming situation. Turn on the light.