Matt Zwolinski is Professor of Philosophy at the University of San Diego and director of USD’s Center for Ethics, Economics, and Public Policy. He is the editor of Arguing About Political Philosophy and, with Benjamin Ferguson, The Routledge Companion to Libertarianism and Exploitation: Philosophy, Politics, and Economics (both in progress). He is currently writing a book on the history of libertarian thought with John Tomasi, and a book on the idea of a Universal Basic Income with Miranda Perry Fleischer.

I wish I were a good cook. But I know that I am not.

I’m not awful. I can follow a recipe and come up with, say, a decent dish of chicken chow mein. As long as it’s a recipe of the rather pedantic, modern sort. “Add ¼ tsp of salt” I can do. “Season to taste,” on the other hand, gives me just enough discretion to gag myself on.

And that, of course, is why I am not a good cook. For being a good cook requires more than merely executing precisely stated instructions like some sort of culinary robot. It involves the ability to understand why those instructions say what they do, and to know when one ought to ignore them, supplement them, or just fill in the gaps. Being a good cook more involves more than just the blind following of rules; it involves a certain kind of wisdom and good judgment of the sort one cannot learn from any book but that of experience.

Political morality, it seems to me, is at least as complicated as Chinese food. Why, then, would we expect that sound political decisions could be made simply by blindly following a small set of rules, let alone a single rule? If we can’t come up with an iron‐​clad rule to tell us how much salt to add to a dish and under what circumstances, why think that we could come up with one that tells us precisely when the use of force is or is not morally justifiable? (Taste for salt is subjective, of course, but that’s not the only problem we face in devising such a rule. We cannot devise an iron clad rule for when one ought to advance one’s knight in a game of chess, even though the outcome at which one aims – winning – is presumably as objective as any other).

Some libertarians think that we have precisely such a rule in the Non‐​Aggression Principle (NAP). And in a recent essay here, I have argued against that belief. But in a sense, there’s nothing especially wrong about the NAP. It’s not as though I think that it’s the wrong foundational rule on which to ground libertarian belief, and that some other rule would do better. The problem is not the content of the rule. The problem is with the idea that libertarianism should be based on any foundational rule at all.

Any rule that purports to provide us with a completely adequate standard for judging matters of political morality is subject to counterexamples. This is true of the NAP. But it’s true of the principle of utility as well. And of Kant’s Categorical Imperative.

Understood as rules that trump all other morally relevant considerations, each of these candidates fail. But understood as principles, they are all – NAP included – eminently sensible.

Consider the following discussion of the difference from a recent paper I wrote with David Schmidtz:

Principles are not like rules. Where rules function in our reasoning like trump cards, principles function like weights. If the appli­cable moral rule forbids X, then X is ruled out, so to speak. In contrast, principles can weigh against X without categorically ruling out X.

Consider an analogy. A home builder might say, in describing his or her philosophy about how to build houses, “You have to minimize ductwork.” Question: Is that a rule or a principle? The answer is that, interpreted as a rule, it would be silly. As a rule, it would say, no matter what weighs in favor of more extensive ductwork, minimize ductwork, period. In other words, zero ductwork!

In fact, though, “minimize ductwork” is a good principle rather than a bad rule. As a principle, it tells home builders to be mindful of energy wasted and living space consumed when heated or cooled air is piped to remote parts of the house. Other things equal, get the air to where it has to go by the shortest available route. This principle will seldom outweigh the principle that the ceiling should be a minimum of seven feet above the floor. That is to say, it is not a trump, but it does have weight. A good builder designs houses with that principle in mind, but does not treat the principle as if it were a rule.

The NAP, too, is a good principle rather than a bad rule. Understood as a principle, as Michael Huemer has recently noted, it is part of the content of commonsense morality that it is wrong to steal, assault, or murder. But that it is always and absolutely wrong to do these things flies in the face of common sense. After all, nonaggression is a sensible principle, but so too is the utilitarian principle that we should do as much good (or avoid as much evil) as possible. And so when we consider whether people ought to be allowed to drive cars (despite the fact that they generate pollution that harms innocent others), or whether a people ought to be able to defend itself in a justified war (despite the fact that conducting such a war runs the almost certain risk of harming or killing innocent persons), almost all of us respond in the affirmative. We respond this way not because we reject the NAP, but because we recognize that it is not the only principle relevant to political morality.

Indeed, when we reflect upon our considered moral beliefs, there seem to be many such principles. For instance, most of us also believe that justice requires that people get what they deserve, and that the basic needs of those with whom we stand in certain relations be met, at least when we can do so at reasonable cost to ourselves.

In some contexts, considerations of need will (or ought to) dominate our moral reasoning, as for instance, in “stranded hiker” type cases where the desperate need of the hiker overrides the right of the cabin owner that no one use his property without his consent. In other contexts, those considerations will be defeated by others that we deem to be more significant. When drivers encounter each other at the intersection of two busy roads, we do not think that the right‐​of‐​way should be determined on the basis of who needs to get to their destination most quickly. After all, no one would get to their destination quickly if making it through an intersection were dependent on their ability to win a philosophical debate. And yet, even in this context, most of us think that someone bringing a severely injured person to the hospital should not be punished for driving (cautiously) through a red light.

It would be nice if we had some kind of underlying “super rule” that told which principle ought to carry the day in which context. Such a rule would make moral reasoning simpler, and relieve of the burdensome responsibility of exercising imperfect judgment in the weighing of principles. Or seem to relieve us of that responsibility, anyway.

But while we can make our moral theory as simple as we wish, that doesn’t do anything to simplify the underlying moral facts that theory is supposed to represent. Morality – even just the sub‐​part of morality concerned with justice – is complicated. As libertarians, we can either ignore that complexity, pretending that considerations of need, desert, and utility are of no intrinsic significance. Or we can embrace it, and argue that our system does better than any alternative at coping with that complexity, and generating reasonable political prescriptions on the basis of all the morally relevant information.

I opt for the latter route, which I suppose makes me a kind of pluralist about justice, and probably about morality more generally too. Embracing pluralism means giving up on the idea that political conclusions can be derived in a neat, airtight way from a foundational moral rule. It means recognizing that good political decisions, like good decisions in cooking or in chess, require the exercise of good judgment. And that good judgment itself is the product of careful reflection on experience and sensitivity to details of context.

All of this makes political decision making harder, no doubt. And perhaps it makes the product of those decisions less certain. But both of these results, I think, should be seen as virtues of the approach rather than drawbacks. As Aristotle wrote, “it is the mark of an educated man to look for precision in each class of things just so far as the nature of the subject admits.” We do ourselves no favors by pretending – to ourselves or others – that political morality is simpler or more precise than it really is. If, then, we are to be libertarians, let us be libertarians with our eyes wide open — willing and ready to look for truth or moral insight wherever it may lie. And let us recognize that a social or political morality devised, constructed, and derived according to a single overarching principle makes no more sense than an economy planned in such a way. Both involve the same hubris, the same close‐​mindedness, and the same fatal conceit.