Darwin's Revolutions
Darwin contributed to biology by establishing the fact of evolution, based on a huge amount of observations, and then proposing a theory to explain one of the most common mechanisms of evolution, which he called “natural selection.” Facts and theories are not steps in any ladder of increasing certainty; according to Gould (1981), facts are the world's data, and theories are structures of ideas that explain and interpret facts. Darwin's work enlightened this difference between the two.
