Charles Darwin was far from the first person to defend the idea that new species originate by a natural evolutionary process. Between 1750 and 1850 the idea had many defenders, including his grandfather. Why did Charles Darwin succeed in convincing his fellow naturalists, when many before him had failed? Based on a decades-long study of his private notebooks and correspondence, this lecture by James Lennox will describe the inductive method that lies behind Darwin’s brilliant presentation of the theory of evolution by natural selection presented in On the Origin of Species