Lord of the Flies' primary message focuses on the root of evil within humanity. Golding uses the boys' struggle on the island away from the comfort of their parents and civilization to draw a picture why how things fall apart--one of the most revealing moments in the novel occurs during Simon's dialogue with the beast:
"Fancy thinking the Beast was something you could hunt and kill! You knew, didn’t you? I’m part of you? Close, close, close! I’m the reason why it’s no go? Why things are what they are?”
Rather than being some outside force of evil on the island, the true nature of the beast , Simon realizes, is within the boys themselves--that human nature is essentially flawed. Without the influence of law and civilization, the boys descend into savagery by the end of the novel.