Editer’s Note: This post is part of a series by philosopher J. C. Lester critiquing Libertarianism.org blogger Matt Zwolinski’s posts on understanding freedom. Here Lester responds to Zwolinski’s “Locke and Nozick on the Justification of Property.” Despite the title, I put Locke and Nozick aside—along with Zwolinski’s comments on them. For the very idea that there can be a “justification of property”, or liberty, or anything else, is a fundamental epistemological error and one that holds libertarianism back. This view is, however, probably more controversial and complicated than anything I have written above. And so I intend to explain it in a little more detail than my previous responses. If critical rationalism is true, as I believe, then the “justification” of any view is an epistemological impossibility. And failing to understand this is a third main serious problem for most libertarians—along with 1) not having an explicit, objective, pre‐propertarian theory of libertarian liberty, and 2) not fully appreciating how human liberty and welfare are systematically connected both conceptually and causally. Therefore, I conclude my responses to Zwolinski by briefly outlining both critical rationalism and how I take it to apply to libertarianism. No theory (or thesis, view, outlook, opinion, argument, proof, etc.) can ever rule out the possibility of a refuting counter‐instance or counter‐argument. With our finite and fallible reasoning facing the infinite worlds of unknown matter and theories, we never know what we might have overlooked. Therefore, theories cannot be justified (or supported, grounded, founded, based, backed, established, proven, etc.). All theories remain conjectures (or guesses, assumptions, suppositions, and so forth). We are obliged to use some conjectures for practical purposes; and not always unrefuted conjectures.[^1] But the only thing we can do with conjectures epistemologically is to criticize or test them as best we can. If we cannot refute them, then they remain conjectures (but they might well be true, of course[^2]). If we can refute them, then we learn something new. However, refutations are themselves conjectural. So no refutation is ever justified either. Fortunately, there is a crucial asymmetry between a justification and a refutation. A conjectural refutation is coherent. It makes sense to say, if this observed phenomenon is a black swan, then “all swans are white” is refuted. Or if this proof is a correctly derived inconsistency, then the theory from which it is derived is false. By contrast, a conjectural justification is incoherent. We could not observe all swans (everywhere and everywhen) being white. Nor could we ‘prove’ the assumptions of an allegedly justifying argument without having an infinite regress, or circularity, or an arbitrary stopping point. It is also worth mentioning that much that is very commonly mistaken for ‘justification’ is actually explanation (e.g., ‘Markets allocate resources efficiently by people bidding for them in proportion to their profitability, whether monetary or psychic’). Such explanations may often be true or useful. But they are themselves conjectures and usually incomplete. How does this apply to libertarianism? It is a conjecture that it is desirable to allow universal interpersonal liberty. Libertarians think that this conjecture is not refuted by any criticisms. All we can do is try to defend it by answering the best criticisms that we can find—and those of critics of libertarianism (occasionally these overlap). What about rights? One might conjecture that rights to liberty are the best rights, and then consider criticisms. What about utility? One might conjecture that liberty is the main cause of promoting utility (in terms of the satisfaction of spontaneous preferences, in particular), and then consider criticisms.[^3] I say “might” because neither of these views can support the universal theory of libertarianism and because a defender of libertarianism might offer different answers concerning rights, or utility, or whatever some specific criticism is about. The point is to attempt the possible: to refute the particular potential refutation somehow (e.g., “Genetic tests indicate that this alleged black swan is really a new species of goose.”) It is not to attempt the impossible: to establish the universal conjecture (e.g., “Genetic tests show that every swan—everywhere and everywhen—is white”). Of course, none of the above is intended to be a justification of critical rationalism and its application to libertarianism. It is, rather, an explanation. And for those interested, I have written at greater length on this matter in various other places. [^1]: Newtonian mechanics are refuted but often useful approximations for practical purposes. The conjecture that people can fly by the power of thought alone, by contrast, appears to be refuted and not worth trying in any dangerous context. [^2]: And either a theory or its negation must be true (assuming the logical law, or principle, of excluded middle). [^3]: I call this the “classical liberal compatibility thesis” in Escape from Leviathan. But David Goldstone points out (private communication) that the “compatibility” of liberty and welfare makes it sound like an unexplained coincidence, when libertarians usually believe that liberty is a major explicable and testable cause of welfare promotion. I am partly inclined to agree. In that case, “classical liberal causality thesis” is possibly clearer. However, some of the overlap is for important conceptual rather than causal reasons, and only “compatibility” seems to cover both.