There are two main strains of libertarianism: rights-based and consequentialist. For rights-based libertarians like Ayn Rand, Murray Rothbard, and Robert Nozick, violating a person’s libertarian rights (also known as “initiating the use of physical force,” breaching the “non-aggression axiom,” or simply “coercion”) is not merely bad, but morally impermissible. Rights-based libertarians are often interested in social science, but social science plays no fundamental role in their defense of a free society. In their view, people can justifiably become libertarians before they ever open an economics textbook —and nothing in the textbook can bring libertarian principles into question.
For consequentialist libertarians, in contrast, violating libertarian rights is not inherently wrong. We should respect libertarian rights because the overall consequences of doing so are good. For consequentialist libertarians, social science is all-important. People cannot justifiably become libertarians until they know enough social science to weigh the overall consequences of various policies against each other. Furthermore, as soon as the evidence shows that coercion has slightly better overall consequences than leaving people alone, consequentialist libertarians must support that coercion.
Counterexamples to rights-based libertarianism are notoriously easy to find. The classics are hypotheticals where a small rights violation leads to vastly better consequences. Is it really morally impermissible to steal a dime to save a person’s life? To steal a dime from each and every person on earth to save the world? Furthermore, if even small rights violations are forbidden, why don’t we need other people’s consent before we vibrate their eardrums by speaking to them—or shoot molecules at their bodies by breathing on them?
Counterexamples to consequentialism are lower-profile, but equally devastating. The classic: Suppose a doctor cares for five patients, each of whom needs a different organ transplant to survive. The doctor also happens to know a perfectly healthy but utterly friendless stranger. The doctor could easily murder the stranger, make his death look like an accident, then use his organs to save five patients’ lives. Consequentialism seems to imply that this murder is not only morally permissible, but morally obligatory. The most a consequentialist could do is appeal to seemingly morally irrelevant facts like, “In the real world, the doctor would be caught.”
Philosophically literate readers of Michael Huemer’s The Problem of Political Authority will feel a strong temptation to place him in either the rights-based or consequentialist categories. At times, Huemer seems to appeal to rights. When he critiques social contract theory, for example, the substance of Huemer’s argument closely parallels Lysander Spooner’s No Treason: The Constitution of No Authority, a long-time favorite of rights-based libertarians. At other times, however, Huemer seems to appeal to consequences:
Return to the lifeboat scenario. The boat is in danger of sinking, unless most of the passengers quickly start bailing water. This time, however, suppose that none of the other passengers are willing to bail water. You cannot perform the task alone, and no amount of reasoning or pleading will persuade the myopic passengers to take up their buckets. Finally, you pull your trusty Glock out of your jacket and order the other passengers to start bailing out the boat. In this situation, regrettable as the resort to force may be, your action seems justified.
If you read Huemer closely, however, you will discover what makes The Problem of Political Authority so remarkable: Huemer offers a genuinely new defense of libertarianism that combines the strengths of the rights-based and consequentialist approaches while avoiding their flaws.
Instead of making a tortured effort to somehow prove that “human nature” or Kantian meta-ethics implies the blanket immorality of violating libertarian rights, Huemer starts with a modest presumption that libertarians share with the rest of mankind: Under ordinary circumstances, attacking a peaceful person or stealing his stuff his immoral. As he explains:
Almost no one, regardless of political ideology, considers theft, assault, murder, and so on morally acceptable… I have made no particularly strong assumptions about these ethical prohibitions. I do not, for example, assume that theft is never permissible. I simply assume that it is not permissible under normal circumstances, as dictated by common sense morality.
For example, almost everyone accepts the moral presumption that stealing bread is wrong. This principle is not absolute: When Jean Valjean says, “I stole a loaf of bread to save my sister’s son,” his justification is credible. Nevertheless, most attempts to rebut the presumption against stealing bread fail: “I stole the bread because I knew I would savor it more than its owner would have,” shows chutzpah, not moral insight. You don’t have to be remotely libertarian to see the inadequacy of such excuses.
After establishing this common ground, Huemer points out the apparent conflict between ordinary morality and state authority. If anyone other than the state acted like a state, we would brand him a criminal. Unlike most rights-based thinkers, however, Huemer does not hastily declare victory after making this point. Instead, he methodically considers the leading attempts to exonerate the state: appeals to social contract theory, democracy, fairness, and consequences.
The first three families of arguments all fall flat, for reasons Huemer’s book explains in detail. When Huemer turns to consequences, however, matters get sticky. After all, he explicitly admits that violating libertarian rights is morally permissible if the consequences of doing so are sufficiently good. How can a mere philosopher emphatically condemn real-world governments after making such an open-ended concession?
Huemer responds with a simple yet powerful observation: when we say “common sense morality allows coercion under special circumstances,” the emphasis should be on “special circumstances.” Continuing with his lifeboat example:
Your entitlement to coerce is highly specific and content-dependent: it depends upon your having a correct (or at least well-justified) plan for saving the boat, and you may coerce others only to induce cooperation with that plan. More precisely, you must at least be justified in believing that the expected benefits of coercively imposing your plan on the others are very large and much larger than the expected harms. You may not coerce others to induce harmful or useless behaviors or behaviors designed to serve ulterior purposes unrelated to the emergency. For instance, if you display your firearm and order everyone to start scooping water into the boat, you are acting wrongly – and similarly if you use the weapon to force others to pray to Poseidon, lash themselves with belts, or hand over $50 to your friend Sally.
The political ramifications:
If, therefore, we rely upon cases like this one to account for the state’s right to coerce or violate the property rights of its citizens, the proper conclusion is that the state’s legitimate powers must be highly specific and content-dependent: the state may coerce individuals only in the minimal way necessary to implement a correct (or at least well-justified) plan for protecting society from the sorts of disasters that allegedly would result from anarchy. The state may not coerce people into cooperating with harmful or useless measures or measures we lack good reason to consider effective.
Whenever Huemer uses phrases like “good reason to consider effective,” readers may feel tempted pigeonhole him as a thinly veiled consequentialist. They should resist this temptation. True, like consequentialists, Huemer has to take relevant evidence from social science into account. Unlike consequentialists, however, Huemer does not need to argue that libertarian policies lead to the best possible consequences. He merely needs to argue that the consequences of libertarian policies are tolerable. As a result, even Huemer’s defense of anarcho-capitalism manages to be both unusually measured and unusually convincing.
For rights-based libertarians, morality is virtually independent of social science. If you have a right to do X, the consequences of X don’t really matter. For consequentialist libertarians, morality is almost entirely dependent on social science. If you know the consequences of X, you can safely ignore anyone who asserts a right to do X. Huemer stakes out a middle ground between these extremes. For most purposes, “It’s my life, so you should leave me alone,” is perfectly adequate. Social science is valuable, however, because it tells us when we can safely dismiss complaints about the overall consequences of free choice—and when we need to take such complaints seriously.
When people criticize The Problem of Political Authority, I often want to quote John Maynard Keynes on Huemer’s behalf:
Thus those who are sufficiently steeped in the old point of view simply cannot bring themselves to believe that I am asking them to step into a new pair of trousers, and will insist on regarding it as nothing but an embroidered version of the old pair which they have been wearing for years.
Huemer’s “new pair of trousers” is a libertarianism designed to be plausible to non-libertarians as well as libertarians.
How does he make his brand of libertarianism plausible to non-libertarians? He starts with moral premises most non-libertarians already accept, argues methodically and transparently, and generously considers a wide range of objections. When social science is relevant, Huemer appeals to mainstream economics, political science, and psychology – not the heterodox approaches that libertarians love so well. While I don’t expect The Problem of Political Authority to make millions of converts, it as broadly convincing as a reasoned argument for an unpopular conclusion can be.
How does Huemer make his brand of libertarianism plausible to libertarians? He escapes objections to rights-based libertarianism by turning the “Non-Aggression Axiom” into a “Non-Aggression Presumption.” He escapes objections to consequentialist libertarianism by taking this Non-Aggression Presumption seriously. The result is a position immune to all of the standard counter-examples to rights-based and consequentialist libertarianism.
As a free bonus, Huemer dulls the urge consequentialist libertarians often feel to stretch the truth, to make stronger claims about the benefits of libertarian policies than the evidence warrants. Thus, libertarians who oppose a war with Iran don’t need to confidently assert, “This war will clearly make matters even worse.” We should just stick with what we really know: “We shouldn’t murder thousands of innocent people unless we have strong reason to believe doing so will make matters vastly better. And we don’t have a strong reason to believe this.”
When libertarians want to appeal to a broader audience, they usually dial down their rhetoric and their radicalism. The Problem of Political Authority dials down the rhetoric, but leaves the radicalism intact. Libertarians don’t need Aristotelian metaphysics, exceptionless moral axioms, or heterodox social science to call the entire status quo into question. Michael Huemer shows that common sense, common decency, and careful observation are more than up to the job.
 See e.g. Ayn Rand. 1957. Atlas Shrugged (New York: Signet); Murray Rothbard. 1978. For a New Liberty: The Libertarian Manifesto. (New York: Libertarian Review Foundation); and Robert Nozick. 1974. Anarchy, State, and Utopia (New York: Basic Books).
 Or even, like Murray Rothbard, a social scientist by profession.
 See e.g. Ludwig von Mises. 1996. Liberalism: The Classical Tradition. (Irvington-on-Hudson, NY: Foundation for Economic Education), and Jeffrey Miron. 2010. Libertarianism: from A to Z>E,?. (NY: Basic Books). Milton Friedman. 1982. Capitalism and Freedom. (Chicago: University of Chicago Press), and David Friedman. 1989. The Machinery of Freedom: Guide to a Radical Capitalism. (Chicago: Open Court) are often seen as canonical consequentialist libertarian tracts, but the authors’ positions are actually more nuanced.
 See e.g. Friedman, 1989, pp.167-200.
 See generally Samuel Scheffler, ed. 1988. Consequentialism and Its Critics. (Oxford: Oxford University Press).
 Michael Huemer, 2013. The Problem of Political Authority: An Examination of the Right to Coerce and the Duty to Obey. (NY: Palgrave Macmillian), p.94.
 Huemer, p.177.
 John Maynard Keynes. 1931. “The Pure Theory of Money: A Reply to Dr. Hayek.” Economica 31, p.390.
 For elaboration on this point, see Bryan Caplan. 2010. “The Common-Sense Case for Pacifism.” EconLog.