The main theme of Lord of the Flies is evil in human nature. According to pessimistic opinion of Golding, humans are evil and even barbaric, and only a thin film of civilization prevents them from falling back into savagery.
Another important theme is violence. A former school teacher, William Golding was familiar with many unpleasant aspects in behavior of well-educated children. So, in the setting of the novel, Golding undertakes an analysis of violence and its outlets (Jack’s love to hunting or tribal reenactment dances that help to channel the excess of emotions).
One more theme is fear and its effects; it is represented by the whole situation concerning the beast and its exploration. Fear is contagious and opens the way to the weirdest of possible beliefs and superstitions (the well-educated British boys are offering a pig to the mystical beast); it even causes the murder of Simon, possibly the bravest boy of them all.