The theory of evolution is perceived by many people, particularly but not only in the United States, as a controversial theory not yet fully demonstrated. Yet, that living organisms, including humans, have evolved from ancestors who were very different from them is beyond reasonable doubt, confirmed by at least as much evidence as any other widely accepted scientific theory. I argue that Darwin's contribution to science goes much beyond the theory of evolution in itself. The theory of natural selection explains the adaptations of organisms, their 'design'. The 'Copernican Revolution' brought the phenomena of the physical universe into the realm of science: explanations by natural causes that can be tested by observation and experiment. Howe...