Science, above all, is a methodology for acquiring testable knowledge about the natural world-the "art of the soluble" in Sir Peter Medawar's apt phrase. It is not and cannot be a compendium of certain knowledge. If the vernacular word "fact" has any currency in science, it can only be defined as "confirmed to so high a degree that it would be perverse to with-hold provisional assent." By this definition, evolution-the observation that all organisms are connected by unbroken ties of genealogy-is as much a fact as anything discovered by science, as well confirmed as Copernicus' claim that the Earth moves around the Sun. Evolutionary biologists argue intensely about mechanisms of evolutionary change (and such meaty debates are the soul of exciting science, the chief sign of its good health), but we all accept the fundamental fact of genealogical connection.
As a methodology for research, science adopts as its cardinal postulate ...
