I posted the following overview (or clarification) of libertarianism on the Conservative Youth Forum. I want to put it up here, too, maybe to spark some discussion on here as well.
As a political philosophy, all you need to be called a libertarian, neo-liberal, or classical liberal, is a commitment to economic liberty and social, political liberty.
Whatever reasons you have to support these views is a separate question that is answered in different ways by different people. To be a libertarian, you need to believe that the government should be super-small. That's it.
In particular, you
don't need some specific story about human nature, about what people are "essentially" like, whether or not we have "rights," what will follow empirically from libertarian institutions, and so on.
You can be optimistic, pessimistic, or neutral about a theory of human nature and still be a libertarian. There is no need to believe that people are essentially good, bad, or otherwise. For instance, as Ken pointed out, you can believe that people are essentially bad, and be a libertarian because you think it would be the worst possible outcome for these bad people to have access to and control institutions like government.
You might also believe that people are "essentially" good and think that a libertarian program follows. I don't think this is a good approach, since if people were essentially good, it wouldn't be such a bad idea to have a government. After all, we get much more done together than apart, and if we didn't have shitty politicians we could count on people to really get more good done than bad. In other words, I think the assumption that people are essentially good may (given some other assumptions) lend itself to non-libertarian conclusions.
It will depend on what else you think follows empirically or philosophically from your human nature assumptions which will determine whether or not you like liberty and small government, or something else. The 'optimist' libertarian will say that we are essentially good, so we don't need the government. Since the government costs money, it is better for us not to spend it on that, and spend our resources on other things. The 'pessimist' libertarian will say that we are essentially bad, so we had better keep these people from the levers of political power. The only way to do that is to restrict the size and scope of the state.
Consider the pessimists who follow the Public Choice School of Economics, a significant proportion of which are libertarians. James Buchanan and Gordon Tullock, the founders of this approach, argued that politicians--just like the rest of us--are self-interested for the most part. That means that they will construct policy to favour special interests, their own, and fill their pockets, all in an effort to get and stay elected. They say the size and scope of the state needs to be reduced and small in order to avoid the massive inefficiency that government brings about.
There is no need to think that libertarians believe in some fairy tale of human loveliness to support liberty. But you would have to be aware of the work of Nobel-prize winner James Buchanan (and Milton Friedman) to understand this.
Secondly, there is no necessity to adopt any particular theoretical approach to get at libertarianism. The most prominent approach is the natural rights approach, but it is hardly the only one. These libertarians say we have "rights," that these rights are "natural," and that they take the following specific form: We have a right to life, liberty, and property. These rights are essentially "negative" (meaning: they don't tell you what you can do, they tell you what you can't do. Namely, the right to life means you can't kill people, the right to liberty says you can't restrict peoples liberty, the right to property means that you can't prevent people from acquiring, keeping, and doing things with stuff.)
I'm not a natural rights libertarian. I see little reason to believe in these rights as metaphysical facts about you and I that everyone can "just see" if they look at us, or think of us, in really special ways. But, whatever, plenty of people think we do have these "rights" and that we have them whether or not anyone actually thinks we do, or governments accept the fact that we have them.
Thirdly, there is no need for a libertarian to be an individualist, or have some specific view about the role other people play in our lives. For instance, I'm no individualist, I'm a communitarian. That means that I think we are "essentially" (at core, or at bottom, or ultimately, or whatever) social creatures with our human relationships being the most important thing.
How does this work? I believe the following: communities form because we are social. Those communities have different avenues to bring their preferences and goals to fruition. One of those avenues is to form civil institutions like charities, informal policing groups, environmental clean-up organizations, and so on. Another avenue is to lobby the government to do these things.
The government, however, is impersonal and divides, rather than unites, communities. When Joe takes care of the orphans on Orphan Avenue, others become aware of it and join his mission. He becomes prominent in his community for this reason. People join or don't join based on their own preferences, and
genuine human ties are built around common purposes. When Joe's informal project is formalized through the government, bureaucracies somewhere else take over these functions. Impersonality follows. Orphans are carted off here and there without the sort of human touch that Joe previously had, and you get a raft of people who don't care a lick about orphans getting these jobs to earn money, not to help orphans.
Of course, of course, of course, there will be deeply sympathetic bureaucrats who actually care about orphans. That's not the point. The point is that some who don't care get involved, and the necessary paperwork and bureaucratic processes of government depersonalize the entire affair.
Potentially genuine human relationships are undermined, and instead of building communities, we undermine them. In addition, those of us who have other projects, or who think money should be spent on other priorities get angry by having to pay for the government orphanage program. Whereas Joe asks for money and builds communities by getting voluntary support, government takes the money without asking and without wondering about the personal circumstances of those whose money is so taken. Witness the conservative hatred of welfare as a great example of this. I've not met a single conservative pissed off that some church group is providing soup kitchens or housing support, and so on. But put those same functions into the hands of government, and you get pissed off people who start talking nonsense about how poor people don't work enough, are lazy, 'deserve' their crappy lives, and so on.
Fourthly, we needn't be philosophical about it either. We can be thorough-going pragmatists and still be libertarians. Milton Friedman, for instance, is pragmatic and still calls himself a libertarian (yup--a libertarian, he does
not call himself a conservative). How might this be possible? Consider the empirical outcomes of economic and social liberty. John Stuart Mill was a libertarian on social issues from a utilitarian/consequentialist point of view. He said the freedom to say and do just whatever we'd like (provided everyone else we plan to do things with or to is game) will result in good consequences. We will get to truth better, we will have experiments in living that others pursue (like being gay, getting body piercings, and so on) that we can use to better inform our own preferences, and we are likely to progress better this way. Meanwhile, a massive pile of economists are libertarians about economics. Friedman argued that economic liberty increases wealth, general prosperity, and the quality of life of everyone who lives under economically free institutions and systems. I think most of us on this list are either economic libertarians, or deeply sympathetic to this outlook, even if we think there are or should be exceptions to this liberty.
The upshot? Libertarianism is a commitment about how the particular institution of government should be and look like. It says nothing (yet) about why you believe that's what the government should look like. I have tried to show that there is an incredible plurality of ways to get to this conclusion, and that none of them is
the libertarian story. You can believe people are good, bad, or otherwise. You can be an optimist or a pessimist. You can believe in natural rights, or not. You can be an individualist, or a communitarian, or something else. You can be a pragmatist and believe in liberty (depending on what you think are the empirically probable outcomes). You can be a consequentialist arguing for the good outcomes of liberty, or a deontological theorist arguing from first principles. You can be a liberal in theory, and a libertarian in practice (yes, you can. Consider the fact that John Rawls himself said, in the preface to the second edition of
A Theory of Justice, that he did not intend to justify the welfare state. You can have a commitment to justice that demands each of us help the poor, the destitute, the homeless, the disenfranchised, and so on, and think that the government is not the right institution to help ease these problems.)
But all of this depends on so many other background conditions, assumptions, empirical facts, probabilities, and so on. At bottom,
all that unites libertarians is a commitment to small government, and the belief that we should be economically and socially/politically free. Nothing else matters to being called a libertarian.