15.5: Creating Scientific Explanations

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Bradley H. Dowden
California State University Sacramento

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The power to explain is a mark of your having discovered the truth. Those who can explain more know more. Hundreds of years before astronauts photographed the Earth, our civilization proved that the Earth is round, not flat. How did it do this? Not by gathering many positive reports from people declaring that the Earth is round while failing to receive any negative reports declaring it to be flat. The evidence was more indirect: the hypothesis that the Earth is round enabled so many things to be explained that otherwise were unexplainable.

By assuming that the Earth is round we can explain why Magellan's ship could keep sailing west from Spain yet return to Spain. By assuming that the Earth is round we can make sense of the shape of eclipses of the moon (they are round shadows of our round Earth). By assuming that the Earth is round we can explain why, when we look away from port with our telescope at a ship sailing toward the horizon, the top of the ship disappears after the bottom, not before. By assuming that the Earth is round we can explain why the sun can shine at midnight in the arctic. All these facts would be deep mysteries without the round-Earth hypothesis, and it would be nearly a miraculous coincidence if all these facts fit so well with an assumption that was false; therefore, the assumption is a fact. The moral is that science is propelled forward by its power to explain.