Hypothesis

In sum, a hypothesis provides the best explanation when it is more ex- planatory, powerful, falsifiable, modest, simple, and conservative than any competing hypothesis. Each of these standards can be met to varying de- grees, and they can conflict. As we saw, the desire for simplicity might have to be sacrificed to gain a more powerful explanation. Conservatism also might have to give way to explain some unexpected observations, and so on. These standards are not always easy to apply, but they can often be used to determine whether a particular explanation is better than its competitors.

Once we determine that one explanation is the best, we still cannot yet in- fer that it is true. It might turn out that the best explanation out of a group of weak explanations isn’t good enough. For centuries people were baffled by the floods that occurred in the Nile River each spring. The Nile, as far as any- one knew, flowed from an endless desert. Where, then, did the flood waters come from? Various wild explanations were suggested—mostly about deities of one kind or another—but none was any good. Looking for the best expla- nation among these weak explanations would be a waste of time. It was only after it was discovered that central Africa contains a high mountain range cov- ered with snow in the winter that a reasonable explanation became possible. That, in fact, settled the matter. So it must be understood that the best expla- nation must also be a good enough explanation.

Even when an explanation is both good and best, what it explains might be illusory. Many people believe that shark cartilage prevents cancer, be- cause the best explanation of why sharks do not get cancer lies in their carti- lage. One serious problem for this inference is that sharks do get cancer. They even get cancer in their cartilage. So this inference to the best explanation fails.