In 1933, Franklin Delano Roosevelt, new president of the United States, said that the "only thing we have to fear is fear itself." Okay, it's a little more eloquent than Piggy's "I know there isn't no fear," but the point is basically the same: the most dangerous thing on this planet is probably fear, especially fear of the unknown. (Need us to be a little more literal? The Cold War was a war of fear: each side was so afraid of the other starting nuclear war that they built up their nuclear capacity, until the entire world could have been blown away if someone's trigger finger had just jerked.) The boys in Lord of the Flies might be afraid of the beast, but that fear turns out to be more dangerous than any beast could possibly be. What they don't know is that they should really be afraid of each other—and of themselves.
Golding suggests that fear—of either the known or the unknown—is the most destructive human emotion.
In Lord of the Flies, fear becomes paralyzing and unbeatable when the boys realize that there's nothing to be afraid of except fear.