Fear is arguably the dominant theme in William Golding's Lord of the Flies. From the moment the boys find themselves alone on the island, fear works quietly and steadily to unravel their fragile order, driving them from reasoned cooperation towards superstition, cruelty and savagery.
Fear of the "beast". The most obvious form of fear is the boys' dread of an imagined monster. It begins with the small boy with the mulberry birthmark who speaks of a "snake-thing", and grows until the beast dominates the assemblies. Because the little ones cannot distinguish nightmare from reality, the fear spreads and hardens into shared belief. The sighting of the dead parachutist, mistaken for the beast, seems to confirm it.
Fear of the unknown and the dark. The island at night, its noises and shadows, breeds terror. Fear feeds on ignorance; the boys people the darkness with horrors of their own making. Golding shows how, cut off from the adult world, the mind manufactures its own demons.
Fear as a tool of power. Jack exploits fear to seize and hold control. By keeping the idea of the beast alive, and by offering sacrifices to it, he binds the boys to himself and justifies his tyranny. Fear becomes the foundation of his savage regime, showing how terror can be manipulated for political ends.
The true location of fear: within. Simon alone grasps the deepest truth, that the beast is not an external creature but the darkness inside the boys themselves: "maybe it's only us". The Lord of the Flies, the pig's head, voices this insight, telling Simon the beast is part of him and cannot be hunted or killed. Fear is therefore ultimately fear of human nature's own capacity for evil.
The consequences of fear. Fear destroys reason and morality. It leads to the frenzied killing of Simon, the hunting of Ralph, and the collapse of every civilised restraint. Piggy's death and the burning island are its final fruits.
Thus fear pervades the novel from first to last, and Golding uses it to reveal how easily terror, whether of an imagined beast or of the darkness within, can reduce human beings to savagery.