The model is often stated as a rule: The simplest solution to a problem is the correct one. This popular description happens to be wrong. Occam’s razor is a guiding principle—not a hard-and-fast rule. Nor is it a preference for the simple at all costs. Rather, it’s a preference for the simple, all other things being equal. Carl Sagan put it well: “When faced with two hypotheses that explain the data equally well,” you should “choose the simpler.”37 In other words, “when you hear hoofbeats, think horses, not unicorns.”38
