Early on, fears rise in the boys, especially the youngest of them, from the trauma of being alone on a deserted island. These fears focalize into fears of the supernatural, primarily the terror of a beast lurking in the jungle and threatening them. The older boys, particularly Ralph, Piggy, and Jack, work together at first to try to dispel these anxieties. In a meeting, Ralph says,
We’ve got to talk about this fear and decide there’s nothing in it. I’m frightened myself, sometimes; only that’s nonsense! Like bogies. Then, when we’ve decided, we can start again and be careful about things like the fire.
Ralph wants them to confront their irrational fears so that they can stay focused on the practical aspects of survival and rescue.
Jack backs up Ralph, saying,
You littluns started all this, with the fear talk. Beasts! Where from? Of course we’re frightened sometimes but we put up with being frightened.
When Maurice starts talking of giant squids hundreds of yards long rising from the sea, as well as the limits of science, Ralph thinks,
this seemed the breaking up of sanity. Fear, beasts, no general agreement that the fire was all-important.
Ralph dreads the loss of rationality and consensus among the boys.
Later, Ralph is under the mistaken impression he has seen the beast, and the belief that it is real frightens him:
“The beast had teeth,” said Ralph, “and big black eyes.” He shuddered violently. Piggy took off his one round of glass and polished the surface.
After Jack lures most of the boys to follow his atavistic leadership, Ralph begins to fear Jack and his followers, the "tribe":
Tired though he was, he could not relax and fall into a well of sleep for fear of the tribe.
Ralph knows that Jack has become a demagogue, like Hitler, plugging into the irrational desires and fears of the boys as well as their need for the security of a dictator. He knows, too, that he is a target and experiences the pure fear of being chased by the mob:
He... became fear; hopeless fear on flying feet.