Perhaps the strongest reason for advocating the establishment of a state or for defending the existence of a state is that only a state can administer punishment fairly.
Most people believe that criminals deserve to be punished.
Most people also believe that criminals who commit equal crimes should receive equal punishments. However, people do not all agree on what the fair punishment should be for any particular crime, and nobody can prove that one particular punishment is more fair than another punishment for the same crime. If individuals were allowed to punish criminals as they see fit, the punishments received by criminals who commit similar crimes would vary, depending on the emotional state, physical capacity, economic resources, and theory of punishment of the individual who administers the punishment. Each individual punisher might believe that the punishments he administers are fair, yet each should, logically, regard all the other punishers who administer different punishments as unfair. Consequently, the overall system of punishments administered privately should be regarded by everybody as unfair.