perfect solution fallacy (nirvana fallacy)

The perfect solution fallacy (aka the nirvana fallacy) is a fallacy of assumption: if an action is not a perfect solution to a problem, it is not worth taking. Stated baldly, the assumption is obviously false. The fallacy is usually stated more subtly, however. For example, arguers against specific vaccines, such as the flu vaccine, or vaccines in general often emphasize the imperfect nature of vaccines as a good reason for not getting vaccinated: vaccines aren't 100% effective or 100% safe. Vaccines are safe and effective; however, they are not 100% safe and effective. It is true that getting vaccinated is not a 100% guarantee against a disease, but it is not valid to infer from that fact that nobody should get vaccinated until every vaccine everywhere prevents anybody anywhere from getting any disease the vaccines are designed to protect us from without harming anyone anywhere.

The nirvana fallacy is often used by climate-change deniers. Again, they do not baldly state: until a perfect scientific study is done that proves with absolute certainty that global warming is being aggravated by human activities and that we must limit fossil fuel use or there will be grave planetary consequences, we should not take any steps to limit the use of fossil fuels. Stated that way, it would be obvious that the claim is false. No scientific study is perfect and nobody can predict the future with absolute certainty. One of the more common tactics of climate change deniers is to note weaknesses, flaws, or errors in models. No model that tries to predict the future about complex things like climate change or deaths from the flu can be 100% accurate. (Note: the attack on predictive models is often a straw man attack; the arguers ignore all the other scientific evidence and reasoning used to build up the case for taking action regarding climate change or vaccination programs.)

The nirvana fallacy is often behind the rejection of science-based drugs and surgery. Again, nobody says a drug must have no possible adverse side-effects on anybody anywhere before it is safe to take. Stated that way, the claim would make one look foolish. But it does not look foolish to refuse to take a drug by listing the long litany of items that have been recorded as possibly happening after taking the drug in question. Nor does it look foolish to reject science-based medicine on the basis of anecdotes about people who allegedly suffered adverse side-effects from a drug. (I say "allegedly suffered" because often all we know is that the adverse event happened after taking the drug. That fact is not sufficient evidence for establishing a causal connection between the two.)

Some people who oppose government welfare programs cite as their main reason the fact that some people on welfare cheat and scam the system. That's true, but there will never be a perfect welfare program. The fact that we read occasional reports about police officers who beat to death or shoot to death mentally ill people for not obeying orders the victims are probably incapable of following does not mean we shouldn't have any police. There will always be police officers who cheat, abuse those they arrest or have in jail, kill unjustifiably, scam the system, etc, but that is not a sufficient reason for abolishing police departments. There will always be superior officers in the military who will sexually, physically, and emotionally abuse subordinates, but that is not a sufficient reason for abolishing our military forces.

I have found one example of an argument where the demand for perfection is stated baldly. Unfortunately, it makes the arguer, psychologist Gary Klein, look like an idiot. Klein writes:

Any enterprise has its limits and boundary conditions, and science is no exception. When the reach of science moves beyond these boundary conditions, when it demands respect and obedience that it hasn't earned, the results can be counter-productive. One example is Evidence-Based Medicine (EBM), which is the scientific idea that I think we should retire....we should only trust EBM if the science behind best practices is infallible and comprehensive, and that's certainly not the case.

It is certainly the case that EBM is not infallible (what is?), nor is it comprehensive (again, what is?), but that is not a sufficient reason for abandoning EBM. (I found this example in an article by Steven Novella on Science Based Medicine.)

In 1969, economist Harold Demsetz used the expression "nirvana approach" to describe what he considered to be a pervasive approach by politicians dealing with public policy: posing a false dilemma where some ideal is pitted as a realistic choice versus some imperfect "institutional arrangement." The policy makers should be comparing realistic choices among "real institutional arrangements." What are the odds of there ever being a perfect solution to any political, economic, or social problem? It will always be a choice of imperfect solutions. The most reasonable approach would be to consider the major pros and cons of realistic solutions, take action if we must by choosing the solution where the pros outweigh the cons, and let the chips fall where they may but be open to instituting change when appropriate.

See also the hidden persuaders.

further reading

the perfect solution fallacy from tvtropes.org, a wiki catalog of the tricks of the trade for writing fiction, but very useful for evaluating non-fiction as well

Demsetz, Harold, 1969. “Information and Efficiency: Another Viewpoint,” Journal of Law and Economics, 12, no. 1.