There are two types of ideas that dominate current public discourse—the contrarian and the counterintuitive. A contrarian idea is one that, whether correct or incorrect, opposes or rejects popular opinion or goes against current practice. A counterintuitive idea is one that is contrary to intuition or to common-sense expectation but is nevertheless correct. Getting the two mixed up can have a detrimental effect on society.
Take, for example, the increasingly popular contrarian-posing-as-counterintuitive idea that locking up more criminal offenders isn’t making people any safer. As the Washington Post‘s Emily Badger writes,
As economists would put it, there are diminishing returns to incarceration. Lock up one criminal in town, and crime will decline. Lock away two, and it will probably decline further. But each criminal in prison yields a smaller and smaller impact outside of it — until finally, there’s no new impact at all. Now we’re effectively imprisoning more and more people with no benefit to public safety.
The first four sentences are perfectly reasonable, but the last sentence draws the wrong conclusion. Let’s create a simple model to show why that reasoning is flawed.