The Contractualists
Why should a government exist at all? This is the basic question that Rousseau, Hobbes and Locke explored. They all agreed that in principle humans had joined in and observed a social contract but they differed on many points.
Hobbes believed that life in the "state of nature" must have been terrible. He imagined before civil society humans mustve been in a war against every individual except yourself. He imagined it was a life of "no arts; no letters; no society and which is worst of all, continual fear, and danger of violent death; and the life of man, solitary, poor, nasty, brutish, and short." He believed to avoid this humans were turn to any form of government over anarchy as a civil society was rationally in their best interests.
Locke was a bit happier (but in my opinion probably not as accurate) he believed the original state of nature wasn't so bad. In fact he made it sound like it wasn't that bad at all. There was tolerance, equality and none of that fear of violent death stuff but why would the people abandon such a Garden of Eden type life? I don't know Locke theorized it was because they couldn't secure anything as their was no money or deeds or courts so everything was uncertain and up in the air. To fix this problem people formed a civil society.
Rousseau believed life in the original state of nature was also pleasant, in fact it was all gravy. He believed prior to civil society we were "noble savages" and it was actually society that corrupted us. He once said man is born free but everywhere is in chains. He wasn't all doom and gloom about society though, he did believe it could improve. He believed a just society would be a voluntary community with a well of its own. He believed the society would have a general will that wasn't about the individual but about the group as a whole. He believed if people were bad it was society's fault and he believed in a good society you should "force men to be free" if they're bad. Sound like totalitarianism? A lot of political scientists see the roots of it in his philosophy.
I do want to add, though I'm trying to be fairly objective here that I believe Hobbes was more accurate than Locke. I think Hobbes was probably right in a general sense. Anyway I'll leave you with this thought: Rousseau laid the groundwork for the French Revolution while Hobbes and Locke laid the groundwork for the founding fathers.
So to summarize I wrote a three part haiku:
Hobbes was violent death,
Locke was property rights,
R and noble savage.
It's an avant-garde haiku.
Suggested Reading:
Leviathan by Thomas Hobbes
Two Treatises of Government by John Locke
The Social Contract, Or Principles of Political Right by Jean-Jacques Rousseau