Inferring and Explaining

ChaPter eIght Darwin and Common Descent When on board H.M.S “Beagle,” as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geological relations of the present to past inhabitants of that continent.Tese facts, as will be seen in the latter chapters of this volume, seemed to throw some light on the origin of species—that mystery of mysteries, as it has been called by one of our greatest philosophers. —charles DarwIn 1 Making Sense of What Is Already Known Te story of Semmelweis is one of a scien- tist confronting a mystery and systematically going out and gathering new data that helped him solve the mystery. Te story of Darwin is very diferent. On the Origin of Species , Darwin’s four-hundred-plus-page “abstract,” is one of the best-argued works in the history of science. He makes a powerful case for, what we shall see, are two monumental theories. Although he was an excellent feld biologist and geologist, and although his experiences on the Beagle were clearly formative, the evidence he presented in On the Origin of Species was not original; nor did it contain cutting-edge discoveries. Darwin’s genius was seeing, I would say, explaining, known facts in original and insightful ways. Te history of science is full of examples where the revolutionary breakthrough comes, not in the laboratory, but in the theorist’s study. Tis is hardly surprising, since when you are trying to make sense of the myriad of facts and results that compose any of the natural sci- ences, the level of generality and abstraction required for the grand overarching theories will seldom, if ever, come from one nicely designed 67