What caused the social collapse in Lord of the Flies?
William Golding's Lord of the Flies is a novel that shows what would happen if innocent children were left on their own in an idyllic environment. Those who believe in the innate goodness of mankind, who claim that crime and atrocities are the result of an environment of poverty or abuse, would expect that such children could form a Utopian society for themselves. Instead, Golding shows that they create a society that rapidly deteriorates into mayhem and murder.
Of all the boys on the island, only three--Ralph, Piggy, and Simon--have a sufficiently strong moral compass within them to resist savagery. Even then, Ralph and Piggy are involved and feel the thrill of the sensual "dance" that results in Simon's murder. Although they quickly try to rewrite history to say that they weren't there, their internal resources of self-discipline and intelligence were not enough to override the drive of their lower passions. In a mock pig-killing ceremony directed at Robert, even Ralph finds that "the desire to squeeze and hurt was over-mastering."
Piggy and Ralph talk about why things break up, and they come to the conclusion that it is because of Jack. However, Simon is the only one who really understands. As early as Chapter 5, when the boys are discussing their fears of the beast, Simon says, "What I mean is ... maybe it's only us." Then, in his conversation with the Lord of the Flies, Simon gets the full revelation: "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?"
The pig's head on a stick is the personification of the depths of darkness that lie within each person. The social collapse that happens on the island is only the outward manifestation of the moral collapse that exists inside each individual boy on the island, just as it exists in each human being.