Here is the best summary, that I know of, of what libertarians of the kind who read and write for Libertarian Home all agree about. We libertarians all believe in:
 

The right of all persons to life, liberty and justly acquired property;

The voluntary exchange of all goods and services; 

Each individual’s liberty to pursue his or her chosen lifestyle, but not to impose it forcibly on anyone else;

Elimination of coercive intervention by the state, the foremost violator of liberty.

Those words come from an introductory pamphlet produced by the Libertarian Alliance, some time in the mid to late 1970s.

It’s all there. Liberty, property, trade, lifestyle freedom but not forcing your preferred lifestyle on others, and hostility to the large tax-and-spend coercive state such as all countries in the world are now more or less burdened with.

This short summary of what we libertarians believe is equally admirable, in my opinion, for what it omits. In particular, it does not say why or how we have each arrived at being libertarians. There are many reasons to be a libertarian, and we argue amongst ourselves about which of these reasons are the best, or even true. 

Some of us, for instance, have arrived at a belief in a libertarian view of what the rights and duties of the individual should be, and consequently believe in whatever wider legal and political arrangements follow from these principles being adhered to. Such libertarians justify the large-scale consequences of libertarianism by showing how these consequences result from right and true principles being applied, in each small-scale case, to the world. Since those principles are right, so also must the consequences of adhering to them be right, no matter what those consequences turn out to be. You can perhaps tell, from the somewhat clunky and off-putting way that I describe this attitude, that this was not how I myself became a libertarian.

 Libertarians of my sort prefer to argue in the opposite direction, from the consequences of libertarianism, to the rightness of the principles that libertarianism consists of. Libertarians like me look at the world, note that the places that most nearly accord with libertarianism seem to be the most attractive and the most productive places, and that the least libertarian places are the worst, and conclude that therefore an even more distilled and more principled libertarianism than prevails anywhere now would be the best way of all to govern human affairs.

 However, the world being what it now is, we libertarians also disagree about how to put our shared ideas into practice. Politics? If politics, then should we join existing political parties, asnd try to make them more libertarian? Maybe we should try to start our own political party? Either way, which political policies of a libertarian sort does it make sense to prioritise? Or, should we perhaps remain apart from day-to-day politics and concentrate on the long-term ideological struggle? In which case, some of us at least should probably be concentrating on getting rich, both for its own sake, and in order to finance such ideological struggles, for instance by helping our most prominent and promising thinkers and scholars to make headway in academia.

 My own attitude to such tactical debates about how to do libertarianism and how to be an effective libertarian is: all of the above. Let each of us choose what his or her preferred contribution to our shared cause can and should be. In other words, I think that we should apply the principles and methods that we urge upon the world, to make the world better, to our own libertarian efforts. We should practice what we preach. Happily, this is how most libertarians already think and act.

 Pieces actually describing what libertarianism is are surprisingly rare at Libertarian Home. But Richard Cary’s posting in 2012, entitled Libertarianism: What I think it is should be mentioned, if only because Carey’s view of how we libertarians agree about a core libertarian curriculum, so to speak, but disagree both about why we are libertarians and about how to be libertarians, is so very like mine: 

We converge at the axiom, but our starting points are different and our conclusions often likewise.

 However, I think that my anonymous Libertarian Alliance pamphleteer from long ago did improve upon how Carey earlier defined “the axiom”:

Libertarianism is an individualistic political philosophy, based on one primary ethical imperative; non-aggression.

 That’s about right as far as it goes, but what does it mean in practice? My preferred and slightly longer exposition of what we libertarians agree about, consisting of four propositions rather than just the one, goes into just enough detail to make it much clearer what “non-aggression” means in practice, and is, I think, the better for it. (But, see what commenter on Cary’s piece, “Lucian”, says about how “individualistic” is perhaps off-putting. And see also what Nico Metten says in his posting about “non-aggression”.)

 Commenters on this posting of mine will say whatever they want to say. But the comments that will most interest me, if any such comments materialise, will be the ones that are about how accurately my quoted definition of libertarianism actually does describe what we libertarians agree about, and what causes some of us to seek out each other’s company, and to regard ourselves as playing for the same intellectual, political and philosophical team, even as we dispute so many of the details. If the summary which I have offered is not accurate, what might be a better one?