In Lord of the Flies, Golding uses allegory to explain how man will behave under different circumstances. He attempts to show how, even the most well-bred people - boys in this case - will descend into savagery and uncivilized behavior. It is the constraints of civilization that prevent the whole world from plunging itself into anarchy.
It is the structure of society that Golding believes helps people conform and adapt to rules. This therefore, effectively keeps 'the beast' that is inherently in all of us, from unleashing its potential.
As the situation on the island becomes more untenable for the boys and they remove themselves from acceptable behavior - preferring to paint faces and hunt - so they are able to show less regard for what rules there are.
Ralph believes in the 'system' and Piggy helps him maintain order but
A belief in organization is not enough.
Jack has recognized what motiates the boys - fear - and, away from the restrictions of adults, he is able to manipulate
and fosters the notion of a beast, then galvanizes his own abilities by giving them an opportunity to hunt, and therefore control their fear
Golding is thus supporting his own notion throughout that man is something of a 'civilized' beast, only managed by man's need to conform.