Now that I've gotten all the preliminaries out of the way, I will finally come out and describe libertarianism itself. It actually starts from some simple premises, and everything is derived from them.
One way would be to say that libertarianism is the political philosophy dedicated to maximizing the rights of the individual. Another way is with the NAP or ZAP, which means "Non-Aggression Principle" or "Zero-Aggression Principle." This means that no person has the right to initiate aggression against another person. And no, owning private property is NOT an aggression. Proudhon's declaration against Earl Grey Tea is nonsense to us. That is a joke, Earl Grey is Proper Tea.
A key word is "initiate". The NAP is not pacifism. A person is completely within his rights to defend himself.
What makes libertarianism fairly unique in the political sphere is that said principle is applied to the government, instead of always carving out exceptions for the government.
Since no person has the right to initiate aggression, no person may delegate that right. Not even if they get together in a large group and do so by voting.
Everything else libertarian derives from that.
It's not that we are anti-government. It is just that while there are various people or groups that feel they do have a right to initiate aggression, one entity does so on a scale far beyond the rest and therefore must be most carefully watched and guarded against. Who killed more people, Adolph Hitler or Charles Manson?
This is why we are in favor of gay marriage and drug legalization. People have a right to do whatever they want as long as they don't violate the rights of others, and it would take an act of aggression to prevent or punish those who wish to engage in gay marriage or drug legalization.
It's also the reason we are in favor of the free market. If two people voluntarily enter a transaction, no third party has any authority or right to say otherwise and it takes an act of aggression to say otherwise.
As much as I understand Libertarians invariably deny the legitimacy of preemptive war (I've always given them credit for that much at least) this falls flat when it comes to implementation.
"Zero aggression" is a valid principle in and of itself and is not something unique to libertarians, nor should it be. It also has the inherent flaw of IDENTIFYING aggression, as in the case of a man who fabricates an aggressive act in order to mobilize an aggressive (and immoral) action. Police officers have already learned this trick with their now infamous "I was in fear for my life!" defense and Israel demonstrates this on a daily basis, justifying their systematic and overwhelming aggression against Palestinians with the claim of Islamist provocation and "We are only defending ourselves!"
Getting a government to go along with a "zero aggression principle" is a laudable goal in its own right, but that hardly sums up the core of libertarianism. That's actually what most people would call "Not being an asshole."
And there's a bigger problem: "Aggression" and "violence" are not actually synonymous when it comes to politics. It's been 200 years since von Clausewitz famously pointed put that "war is the continuation of politics by other means." So if a government aggressively seizes your property but does so without the explicit use or threat of violence, is this no longer aggression? If a corporation performs a hostile takeover or a leveraged buyout of its competitors... not aggression? If a manufacturer of shoes deliberately sells a superior product at a financial loss to every store in town SPECIFICALLY for the purpose of driving his competitors out of business -- and futhermore, proceeds to take over their shops and properties in order to "save" them from the bankruptcy he himself drove them to -- is this not aggression?
In the United States right now we have a government that has effectively legalized corruption at every level of government in the form of a campaign finance system that welcomes private contribution with little or no accountability; you can drive up to Capitol Hill with a dumptruck full of money and a Lockheed Martin logo on the side of it and announce "I'll give five million dollars to the campaign of every senator who votes to triple spending on the
Joint Strike Fighter." If I were to deliver some "protected speech" to the County Sheiff('s campaign fund) in exchange for him telling his deputies to take a coffee break whenever you and your family call 9/11 (a fact which I have "accidentally" made known to every petty crook in town) are you telling me that isn't aggression on my part?
There are various ways to disenfranchise and oppress people and not all of them have to do with violence. People who have the means can find another way to compromise their enemies; violence is merely the last refuge of the incompetent.