Ralph's pack represents God or holiness. Simon seems the most holy of all the boys on the island. He is a pacifist, comes to the aid of others and keeps his innocence and purity. Ralph's pack is civil and relies on the structure of rules. Ralph and Simon use their power to protect the younger boys and advance the good of the group.
Jack's pack is the complete opposite. They represent Satan and demonic forces. They are vulgar, blood-lusting, impure, corrupt, violent, evil little boys. They act completely on their evil animal instincts, doing only what pleases them without regarding any morals. Jack and Roger use their power to gratify their own needs and treat the littler boys as objects for their own amusement.
Golding's message to the readers is portrayed through this contrast, it represents the bigger picture. Golding portrays the evil that corrupted the boys, a natural result from their increasing openness to the innate evil and savagery that had always existed within them. Golding is implying that civilization can mitigate but never wipe out the innate evil that exists within all humans beings. This touches upon Christianity in a sense that we are all born into sin and born into a sinful, corrupt world due to the first sins of Adam and Eve. This struggle that he hints at, the struggle in us to control our sinful, evil nature parallels the invisible battle the Bible mentions. The invisible battle is the spiritual battle between God and Satan and is invisible because we cannot see what is happening. In reality there are demonic forces working against us and God's forces shaping us and guiding us through life. The Lord of the Flies really signifies this, as we read the boys fall at the evil forces within them and Ralph and Piggy cling to moral goodness and civilization.
