What is the purpose of government?

Imagine a world without governments. Think back hundreds and thousands of years, early humans, sparse populations, no mail or even currencies, just people, living their lives and trying to get by. Somebody says to these non-citizens, "Hey, I've got a great idea. Let's form a government!" What justification would be offered to entice people into becoming citizens, giving a portion of their crops to a tax collector, limiting their freedoms, bowing to the will of a monarch or a their fellow citizens? Pretend for a moment that the citizens aren't conquered or forced into citizenship; they are voluntarily subjecting themselves to government. Why? Really think about this for a minute.

Your answer forms the essence of your underlying beliefs about the purpose of government. The reasons I come up with are, first and foremost, protection from harm, senseless violence, theft, and murder. Establishment of reasonable laws that allow the most people to enjoy continued life and freedom from harm so they can continue to produce, to be family members and community members, without fear of having all that they have earned and produced taken from them unjustly. Establishing and training an army to defend against invasion would also fall under protection from harm.

The second reason I imagine is enforcement of contracts, establishment of currency, and similar rules that allow people to trade safely and fairly. I call this facilitation of commerce. If I promise to give you seeds now in exchange for food later, and you don't provide them, I may never trade seeds again. Then the only people who can farm are the ones who have something to trade in hand, right now.

I don't think people formed governments to provide sustenance to their neediest neighbors - they can do that without government. Even if they don't want to find the needy neighbor themselves, churches and other charities handle gifts of kindness quite well. I imagine a group of villagers discussing government and, if the topic of welfare came up, I imagine five of them saying "hey, Joe only needs welfare because he's lazy. If he wants food, send him over and I'll put him to work, and Jimmie - poor, old childless widower Jimmie - he should of put somethin' back when he was younger, but what's done is done. We all take turns over there, bringing him food and slopping his hogs. We don't need no government to do that!" (I don't think governments formed to provide mail services, since such a thing was barely contemplated and only affordable to the very wealthy, not that I object to the postal service - by providing a consistent means of giving legal notice, it facilitates commerce. There are plenty of new government roles that fall under the facilitating commerce and protecting from harm.)

So given my belief that the number one most important function of the government is protecting us from harm, I am disgusted and outraged at the laxity of law enforcement, the non-punitive nature of prison, and the failure to prosecute or even investigate so many crimes. Similarly, I think that military aggression is a breach of governmental purpose, since it unnecessarily puts citizen soldiers in harms way (and I say this in global terms, without any particular meaning about any current military action by any nation). Citizens have every right to ask whether a military action, over an event that does not put citizens in direct risk of harm right now, is a defensive or offensive move.