Libertarianism is a political philosophy, not a complete system of ethics or metaphysics. Political philosophies address specifically the state and, more generally, justice in human society. The distinguishing characteristic of libertarianism is that it applies to the state the same ethical rules that apply to everyone else. Given that murder and theft are wrong-views not unique to libertarianism, of course-the libertarian contends that the state, which is to say those individuals who purport to act in the name of the common good, has no more right to seize the property of others, beat them, conscript them, or otherwise harm them than any other institution or individual has. Beyond this, libertarianism says only that a society without institutionalized violence can indeed exist and even thrive.
For some exceptionally Christ-like people no demonstration of feasibility is needed. Doing what is right is enough, regardless of whether it brings wealth or happiness or even daily bread. But most people are not like that; they want security and prosperity-they ask, not unreasonably, not only "is it right?" but "can it work?" Following upon this is a tendency to deny that necessary evils are evils at all. Yes, the state seizes tax money and jails those who do not pay, actions that would be denounced as gangsterism if undertaken by a private organization. But if the only way life can go on is to have the government provide defense and other necessities, such expropriations might have to be called something other than robbery.
Moderate libertarians say just that. They propose that the state should do those necessary things that it alone can do-and only those things. Radical libertarians contend there is nothing good that only the state can provide-even its seemingly essential functions are better served by the market and voluntary institutions. The differences between thoroughgoing libertarians and moderates are profound, but the immediate prescriptions of each are similar enough: cut taxes, slash spending, no more foreign adventurism.
The article goes on to explore libertarian solutions in more detail. I recommend reading it. Read this article