William Golding credits his experience in WW II as a turning point in his life when he realized the potential for evil that each of us possess.
"The single event in Golding's life that most affected his writing of Lord of the Flies, however, was probably his service in World War II. Raised in the sheltered environment of a private English school, Golding was unprepared for the violence unleashed by the war."
From his observation of the events of WW II Golding became convinced that circumstances could cause each one of us to become inescapably evil. It was through this understanding that he devised the theme for his wildly popular novel "Lord of the Flies."
He also used his experiences as a teacher to develop the basis for the characters in the book.
"Sir William recalled that as a teacher he once allowed a class of boys complete freedom in a debate, but he had to intervene as mayhem broke out. That incident and his own war experiences inspired "Lord of the Flies."
The two ideas that are developed in the book about human nature and mankind revolve around the possibility of the breakdown of all order in society. Golding imagines an environment which he creates in "Lord of the Flies," providing circumstances that challenge the existence of a group, and examines the reactions of each person to those circumstances.
He makes a point in the book to illustrate the capacity of the most well-behaved and mannered boys, English schoolboys from a fancy prep school, who regress back into savages when all authority and supervision is removed and they are allowed to make their own decisions.
Part of the decision-making has to do with basic, primal survival, which Golding offers can bring out the primitive nature in all of us.
Finally, Golding comments that society's restraints, its laws, order and barrier to total chaos is really very thin. As a matter of fact, he tells us in his allegory, that given the right circumstances, such as those depicted in the book, society could easy revert back to a much more primitive state where survival, kill or be killed, governs the streets.
Golding is making a comment on the relationship that people have with each other and how easily those relationships can become unimportant when one's basic survival is at stake that man's capacity for evil is limitless.
However, Golding was not an absolute pessimist. He actually believed in the goodness in mankind.
"Describing his own work, Sir William said, "I am not a theologian or a philosopher. I am a story teller." Despite his reputation for pessimism on human nature, he said, "I think good will overcome evil in the end. I don't know quite how, but I have that simple faith."