We tend to think of medicine as a science, but for most of human history it has been scientific-ish at best. In the first episode of a three-part series, we look at the grotesque mistakes produced by centuries of trial-and-error, and ask whether the new era of evidence-based medicine is the solution.

Some of our most important decisions are shaped by something as random as the order in which we make them. The gambler's fallacy, as it's known, affects loan officers, federal judges -- and probably you too. How to avoid it? The first step is to admit just how fallible we all are.