Conza

No-one makes clear what libertarianism is better than Stephan Kinsella. Although this passage by Murray Rothbard is hard to surpass:

• Libertarianism is not and does not pretend to be a complete moral, or aesthetic theory; it is only a political theory, that is, the important subset of moral theory that deals with the proper role of violence in social life… Libertarianism holds that the only proper role of violence is to defend person and property against violence, that any use of violence that goes beyond such just defense is itself aggressive, unjust, and criminal. Libertarianism, therefore, is a theory which states that everyone should be free of violent invasion, should be free to do as he sees fit except invade the person or property of another. What a person does with his or her life is vital and important, but is simply irrelevant to libertarianism.
  — Myth and Truth About Libertarianism

That is essentially libertarianism in a nutshell. The above definition provides the big tent perspective. As long as you are attempting to apply the non-aggression principle there can be general agreement about most conclusions. However, what one bases their justifications on does matter otherwise the agreement is merely superficial. There is no problem with fellow travelers who differ with their epistemology as long as they are radical abolitionists.

Put simply libertarianism begins from first principles with the concept of self-ownership, and original appropriation which necessarily leads to the non-aggression principle. The a priori of argumentation, or argumentation ethics offers the praxeological proof which establishes self-ownership as an axiom. It serves as a negative critique of justifiable norms. It bounds the scope of norms that can be consistently justified without pain of contradiction.

• Here the praxeological proof of libertarianism has the advantage of offering a completely value-free justification of private property. It remains entirely in the realm of is-statements and never tries to derive an “ought” from an “is.” — Hoppe, Economics and Ethics of Private Property, p345.

• My entire argument, then, claims to be an impossibility proof. But not, as the mentioned critics seem to think, a proof that means to show the impossibility of certain empirical events, so that it could be refuted by empirical evidence [such as the existence of non-libertarian societies-RPM and GC]. Instead, it is a proof that it is impossible to justify non-libertarian property principles without falling into contradictions … empirical evidence has absolutely no bearing on it. — Hoppe, p406.

Libertarianism is meta-normative, it establishes what you have a right to do. It does not say what you ought or should do. In this sense, being an axiomatic-deductive legal theory based on action it is not a part of ethics at all. [1], [2], [3], [4].