Some fears are nearly-universal, or just quite wide-spread. The dark, heights, blood, enclosed spaces, fire, snakes, spiders, psychopaths, loud sounds, pain, death, monsters, humiliation, loneliness, complete emptiness; these fears have always been with us. They are the dangers our early ancestors faced, and their shadows still haunt our nightmares. Most people are a little nervous about such things — not many people could walk on a glass bridge over the Grand Canyon without any railings.