Philosopher Matt Zwolinski accepted my invitation to reply to my open letter  to him. I’m pleased to share with you here Matt’s reply in full:
I’m grateful for your thoughtful response  to my tweet, and for the subsequent contributions to the conversation from Dan Klein  and David Hart , as well as your personal friend. I’ve been thinking a lot about how libertarians have responded to COVID, and trying to make sense of the persistent disagreement among people who hold so much else in common. Not only are libertarians all over the place in terms of the preferred policy response to COVID – with some favoring lockdowns, some favoring mask mandates, and some favoring virtually no government response at all – but every side in the debate seems to be utterly baffled by every other. Many of the posts at Cafe Hayek suggest that those who favor restrictions on businesses and individual association have abandoned the core insights of libertarianism. Meanwhile, Tyler Cowen can’t understand  why libertarians are so much less willing to accept restrictions on individual liberty now than they were in 2014 when Ebola was a threat.
After giving it much thought, I think I finally understand what’s going on here. The reason that libertarians disagree with each other so much about the best policy response to COVID is, I think, the same reason libertarians disagree with each other about the best policy response to climate change. Libertarian theory, by itself, simply isn’t much help in figuring out what to think about problems like these.
One of the core – if not the core – libertarian insights is an idea that has sometimes been called the “moral parity thesis ” – the idea that if something is wrong for an private individual to do, it’s wrong for an individual or group of individuals in government to do as well. Stated that way, the idea sounds obvious, almost trivial. But as philosophers like Michael Huemer  have shown, when applied consistently, it yields radically libertarian implications. It implies, in the words of Murray Rothbard,  that “war is mass murder, conscription is slavery, and taxation is robbery.” In these cases, libertarianism provides us with moral clarity by reducing apparently complex phenomena to simpler cases where our intuitions are clearer.
But what does this idea tell us about a genuinely complex phenomenon like global climate change? If the scientific consensus is correct, and human activity is causing climate change that will (if not adequately addressed) cause serious harm to future people, then there’s a good  case  to be made that something has gone wrong from a libertarian perspective. People now are acting in a way that is causing harm to other people’s bodies and property. Doesn’t that violate the Non-Aggression Principle?
Well, maybe. The problem is that climate change is a phenomenon marked by two characteristics with which, to be frank, libertarianism doesn’t deal with very well. The first is risk. If I club you over the head and take your money, there’s no question that I’ve violated your rights. But what if I merely engage in an action that imposes some risk of harm on you, like driving under the influence of alcohol (or driving at all, for that matter!), expelling pollutants from my smokestack (or my lungs!), or burning fossil fuels? Libertarianism, as such, simply doesn’t have a good canonical answer to these questions. Barring all risky activity would grind civilization to a halt. Disregarding risk is lunacy. And trying to distinguish between “reasonable” and “unreasonable” risks threatens degeneration into utilitarianism .
The second characteristic of climate change is that whatever negative effects it produces are the unintended consequence of a large aggregation of individual decisions, none of which is necessarily harmful in itself. In that way, climate change is a kind of spontaneous order – though unlike the spontaneous order of market coordination, it’s a harmful order rather than a beneficial one. What should libertarians say about such phenomena? If Jones acts permissibly in performing action X, does his action become impermissible by the mere fact that 100,000 people also perform X, and that the aggregate result of their action is imposition of harm on Sam? Answering yes seems to run afoul of the spirit (if not the letter) of the moral parity thesis. Answering no, in contrast, seems to leave individuals’ bodies and property vulnerable to potentially seriously harmful invasion by others.
I’ve written elsewhere  about these issues as applied to the question of environmental pollution. But it’s pretty obvious that contagious diseases such as COVID raise precisely the same questions. Gathering with many others during a pandemic in a restaurant, or a mass protest, doesn’t automatically harm them. But it poses a certain risk of harming them. And, from a public health perspective, no single individual’s action is going to have any measurable impact on the spread of the disease or the strain on the country’s medical system. But the aggregate impact of individuals’ decision makes all the difference. So going to that restaurant, or that protest, isn’t exactly like punching somebody in the nose. But it’s not exactly unlike it, either.
Of course, the moral parity thesis isn’t the only libertarian insight. David Hart’s points about government failure are well-taken, as are libertarian insights about the ability of individuals to self-organize to accomplish public goals. (As Nozick reminds us, “people tend to forget the possibilities of acting independently of the state.”)
Still, when faced with problems like climate change and COVID, it should come as no surprise when libertarian responses are all over the map. These simply aren’t problems that libertarian theory is especially well-suited to address. And so libertarians, in seeking to address them, wind up falling back on their own personal values, preferences for risk, and assessments of the empirical evidence. Since libertarians presumably disagree amongst themselves on these matters as much as they disagree with anyone else, so too are their views about policy.