In chapter four, Maurice and Roger run onto the beach, where the littluns are playing, and Maurice throws sand in Percival's eyes. As Maurice runs away, Percival begins to whimper, and Golding writes,

In his other life Maurice had received chastisement for filling a younger eye with sand. Now, though there was no parent to let fall a heavy hand, Maurice still felt the unease of wrongdoing. At the back of his mind formed the uncertain outlines of an excuse. He muttered something about a swim and broke into a trot (84).

Golding is commenting on civilization and how Maurice would have been chastised for unnecessarily harming another person. In the society where Maurice was raised, rules and regulations were in place to prevent individuals from harming others. Civilization is founded on institutions that protect innocent individuals and punish people for breaking laws. Maurice's brief, instinctual excuse reveals that he is conditioned by society to not offend or harm others.

However, Maurice is on an uninhabited island, where rules and regulations do not apply. On the island, Golding depicts how the boys revert back to their primitive nature by acting like brutal savages. Maurice's minor act of throwing sand in Percival's eyes depicts how he and the other boys are gradually becoming more savage and distancing themselves from the rules and regulations they were once conditioned to follow.

Essentially, Golding is using Maurice as an example of what will happen to children (and, in turn, the human race) if there are no rules or guidelines to direct our actions.  In this scene, Maurice is beginning to represent the chaos that will ensue if there is nothing to guide our moral behavior. 

On the island, rules are gone.  Ralph is trying to keep order; however, there is no easy way to maintain it.  The children are enjoying the freedom of no parents or teachers too much and Maurice is representing the turning point of going from a civilized society into one where there is no controlling factor.  The quote is showing that at one point, Maurice would have known his actions were wrong; but now he doesn't really care.

 I believe that in one of his interviews, Golding said that he chose boys to be the main characters (instead of men and women) because 1) Golding was a boy at one point and 2) adults were too formed in their ways for there to be any lasting effect.