It isn’t in the group’s best interest if they can’t trust one another. If someone is lying, stealing, killing, or lusting after someone else’s mate, conflict will ensue and the transgressor will be booted out. It is hard to survive in the world alone, especially if you suck at hunting or gathering.
In groups larger than one-hundred, it is imperative to have some form of social contract with rules that are enforceable and enforced. The golden rule of most societies can be boiled down into the loose statement: “Treat others the way you want to be treated.” This isn’t effective if you’re visiting a community of purple people eaters.
Ancient Egyptians had a long list of “I will not ...” statements in their Husia. Jews and Christians embraced commandments which included admonitions to not worship different gods or idols, to not lie or bear false witness against a neighbor, to not murder, commit adultery, steal, or covet their neighbor’s wife.
In your story world, your characters will be subject to the rules of their society's contract. If Dick breaks those rules, there will be consequences. He may fight to change the rules or reveal the dark side to one of his society’s rules.
If you write fantasy or Science Fiction, develop your own ten commandments for your story world. How are they enforced? What are the consequences for breaking them? Are some infringements more serious than others? Are some ignored on a routine basis without consequence?
In The Hunger Games by Suzanne Collins, the citizens of District 12 aren’t supposed to hunt outside the fence, yet Gale and Katniss do so regularly. Because they transgress, Katniss is better prepared to survive the Hunger Games. Breaking the social contract benefitted her. Katniss and Peeta break the contract again at the end of their first Hunger Games by refusing to kill each other, which sets up the conflict for the second book in the series.
Think about your story. Have you directly or indirectly explored social contracts in your story world? Have you put it to work for you in terms of complicating your characters’ lives? Have you utilized transgressions and punishments?
For more information on crafting believable obstacles, pick up a copy of Story Building Blocks II: Crafting Believable Conflict in print or E-book version.