What are the "end of innocence" and "the darkness of man's heart"?
Explain the irony of: The navy cutter was attracted to the island by the fire that Jack built to "smoke out" Ralph and It's wartime and the boys are rescued by a military ship.
In the novel 'Lord of the Flies' William Golding sets out to examine whether evil is present in human beings through 'Nature' or 'Nurture' - that is whether it is brought on by the circumstances in which they live or grow up, or whether the level of it's power is already set at birth. Given what we now know of human genetics that William Golding did not have the benefit of knowing - this is a very interesting idea. If the 'Nurture' idea is right, then the boys surely have most things going for them (religious school, so-called civilized society,attentive parents and a good education.) However, as soon as artificially imposed restraints (rules,bedtimes,washing,manners etc) are removed by their freedom from adult conventions, the guidelines and outward symbols of their civilized background fall away, leaving only the end of their childhood innocence and the dark heart of mankind - except for one or two.
Golding sets his story on an uninhabited island to explore his theme of good vs evil. He debunks the idea that it is society that makes men evil because there is no society on the island. He uses young boys because they are the closest thing to innocence - they have not had time to grow up and become ruined by the corrupting nature of society. In spite of the lack of society, however, the boys turn evil anyway, proving that evil is within us, not outward. The human heart is wicked. This is a Christian viewpoint - that man is basically fallen, cannot save himself and is in need of a savior. Darkness is within all of us, hence the darkness of men's hearts.
The novel is set in wartime when Europe is on the verge of nuclear war. In reality, the novel was published in the early 50s, so not too long after the end of WWII and during the Cold War. War is an evil product of our society. Jack builds a fire to smoke out Ralph, but instead, it brings the military. So the evil, innocent boys are rescued by a product of the evil society, the military. That is the irony.
The boys start out innocent and try to do what is right, but in the end, they lose their innocence because their dark, evil hearts take over. This is the loss of innocence and it is one of the major themes of the novel. Golding shows how the loss of innocence is due to the evil in men's hearts, not the society in which they live.
Read about the novel here on enotes.