If we were omniscient and had infinitely fast and perfect computers, perhaps we could use quantum mechanics to explain chemistry, biology, economics and psychology. In reality, no amount of quantum mechanical theorizing can explain how molecular aggregates coalesce to give rise to self-replicating assemblies, let alone how these assemblies acquire the capacity for consciousness, introspection and purposeful action.

Now imagine someone who has started out with the honest and admirable goal of trying to apply quantum mechanics to understand the behavior of a "simple" biological system like a protein. He knows for a fact that quantum mechanics can account for (not explain) all of chemistry- the great physicist Paul Dirac himself said that. He has complete confidence that quantum mechanics is really the best way to get the most accurate estimates of thermodynamic free energy, solubility, molecular charges and a variety of other important chemical properties for his favorite protein.

But as our brave protagonist actually starts working out the equations, he starts struggling. After all the Schrodinger equation can be solved exactly only for the hydrogen atom. Even a simple protein constitutes a system that is infinitely more complex. The complexity forces our embattled savant to make cruel approximations at every stage. At some point, not only is he forced to commit the blasphemy of using classical mechanics for simulating the motion of the protein, but he also has to stoop to using empirical data for parameterizing many of his models. At one point he finds himself fighting against the Uncertainty Principle itself!

In the end our hero is chagrined. He started out with the lofty dream of using quantum mechanics to create an atomic-level description of his favorite protein. He ended up instead with a set of approximations, parameters from experiments, and classical mechanics-derived quantities which were required simply for explaining the features of the system. Prediction was not even an option at this point.

But his colleagues were delighted; long experience had taught them that in most cases the best you can hope for are useful models and not accurate theories. The patchwork model actually gave fairly useful answers. Like most models in chemistry, it had some explanatory and predictive value. Even though the model was imperfect and they did not completely understand why it worked, it worked well enough to spit out useful numbers. But this modest degree of success held no sway for our bright young scientist. He stubbornly insisted that if only we had an infinitely fast computer and an unlimited amount of time, quantum mechanics would no doubt have been spectacularly successful at predicting every property of his system with one hundred percent accuracy. Maybe next time he should just wait until he gets a perfectly accurate computer and has an infinite amount of time.

I state this parable to illustrate what I think is a rather unwarranted swathe of criticism that you occasionally hear from libertarians about the financial crisis during the last few years. The reasons for the financial crisis are many, probably more complex than the laws of quantum mechanics, and society will surely keep on debating them for years. But one of the most common reasons cited by libertarians (usually in the form of a complaint) for the failure of the economy is that we should not blame the free market for what happened because we didn’t actually have a free market. If only we had a chance to have a perfect free market (or at least freer than what it is), things would take care of themselves. Not surprisingly, this line of argument quickly leads to the case for less instead of more regulation.

Notwithstanding the fact that this argument inches uncomfortably close to arguments made by the most vocal proponents of socialism during the twentieth century (“There was nothing wrong with the system per se, only with the way it was implemented”), I think the argument is fundamentally misleading. Yes, maybe a perfect free market wouldn’t have led to the crisis, but that’s like our young chemist saying that infinitely accurate computers and approximation-free quantum mechanics would not have led to the kind of imperfect models that he ended up with. The problem is that there are so many obstacles in the application of quantum mechanics to a real-life chemical system that we are simply forced to abandon the dream of using it for describing and predicting such systems with speed and efficiency. Unless we come up with a practical prescription for how quantum mechanics is going to address all the obstacles in a real-world system without making approximations, it seems futile to argue that it can really take us to the nirvana of sixteen decimal places.

To me it seems that libertarians are ignoring similar obstacles in pursuit of their dream of a perfect free market. What are these obstacles? Most of them are actually well known: There’s imperfect competition because of the existence of inherent inequalities, leading to monopolies. There’s all that special interest lobbying, encouraged by politicians, which discourages true competition and allows monopolies to get a head start. There's dispassionate cost/benefit analysis by corporations that often leads them to pollute the environment to their heart's content. There’s information asymmetry, which simply keeps people from knowing all the facts.

But all these problems are really part of a great stumbling block- human nature itself. All the obstacles described above are basically the consequence of ingrained, rather unseemly human qualities- greed and the lust for power, the temptation to deceive, and a relentless focus on short-term goals at long-term expense. In reality, many obstacles in the way of a truly free market are put there not by zealous government regulators but by the inconvenient inequalities and stresses endemic in any complex system. I don’t see these qualities disappearing from our world anytime soon.

Now of course, I do agree that the free market was invented to curb some of the worst excesses of these inequities, and it has worked remarkably well in this regard. But the approach has limitations. Maybe libertarians need to understand that the last vestiges of the dark side of humanity can never be exorcised since they are an indelible part of what makes us human. So unless we come up with practical solutions to the problem of human nature itself - a difficult goal, to put it mildly - it’s rather futile to keep on chanting that all our problems would be solved if only we could somehow make these inherently human qualities disappear.

The final argument that libertarians usually make is this: Just because there are obstacles in the way of a goal that may seem insurmountable, it does not mean we should not even try to achieve perfection. Now that’s a perfectly laudable attitude, but the problem is that unless you come up with a practical solution for all the problems that you face on the way, your goal is just going to remain an abstract and unworkable ideal, not exactly the kind of solution that's desirable in the practical arenas of politics and economics. Politics especially is the art of the possible, an endeavor where imperfect solutions which all sides can agree upon are far more preferable to abstract, idealized solutions on which it’s impossible to have consensus (just witness our current political gridlock). More importantly, sometimes a relentless drive toward one goal at the expense of everything else creates problems of other kinds; the science analogy in our previous example would be unimaginably expensive calculations, scientists laid-off because of the lack of results, overheating of the computers leading to fires etc. In case of economics we have all seen these problems.

Personally my main problem with "strong" libertarianism is that it often fails to consider the other aspects of the system, instead looking at every problem exclusively through the lens of lower taxes and greater market freedom, as if resolving these variables will take care of everything else. But that's not the case. There’s the well-known problem of externalities and unintended consequences, there’s the problem of unregulated firms getting ‘too big to fail’ and there’s the persistent problem of growing income inequality; all these problems will still exist to varying extents in a libertarian's perfect world because they are built into human nature and the workings of complex systems. Surely we have to admit that these are real issues too.

So what should libertarians do? Well, didn’t our intrepid quantum mechanic grudgingly accept the intervention of approximations and parameterization in his pursuit of the perfect theory of protein function? These approximations seemed ugly but he had to use them to circumvent the intrinsic limitations of quantum mechanics. Similarly, perhaps free marketers could realize that at least in some cases government intervention, no matter how ugly it may seem, may be the only way to reach a workable goal. It may not be the best of all worlds, but it could be the least of all evils. What would have happened if our bright young scientist had kept on insisting that he wouldn’t budge an inch if he were forced to use anything other than approximation-free quantum mechanics? He would have ended up with nothing. And in economics even more than in chemistry, a model that partly works is better than a model that does not exist. As Churchill put it, “Sometimes it’s not enough to do our best; we need to do what’s necessary”. It's an adage that free marketers need to ponder.

This is a modified and updated version of a post I previously wrote on The Curious Wavefunction blog.