"There are no laws, and there is no one to enforce moral behavior. Each man must provide for himself all things, including defense. Each must fear for his life at all times, and even sleep, which is not optional for individuals, carries a risk of death. The individual can be killed, and he can be killed instantaneously. He is also capable of killing, and the strength of each is close enough that even the weakest can kill the strongest.(Tom McCarthy)" What Tom McCarthy was describing is the state of nature. In the state of nature people kill, steal and deceive selfishly for their own continued existence. The purpose of government is to control the violence that is apparent in human nature. .
Humans understand they are naturally bad. "When taking a journey, he arms himself when going to sleep, he locks his doors- People do not trust others because they know that they themselves are inclined to steal and kill for personal benefit.
The perfect government is one in which people understand why they must not kill, and so will not kill. Unfortunately, people are very reluctant to change these instincts. The only way to stop this violent nature is to make people scared of doing these things. As Thomas Hobbes stated in Leviathan, " during the time men live without a common power to keep them all in awe, they are in that condition which is called war, and such a war as is of every man against every man." A government must be set up in such a way so that people will not "war." Because people refuse to understand why human nature is unmoral, governments must scare its people into doing the morally correct thing. In most cases, governments use the knowledge that people want to live to their advantage by threatening lives (death penalty). Such a tool to control people is not only just, it is necessary. Without the fear of death, humans will resort to their natural instincts of greed and selfishness.