‘Darwin as a scientist’ describes Charles Darwin as a theoretical scientist. Necessarily, scientific theories are not born in a vacuum: a specific issue, fact, or collection of facts has to arouse the scientist's attention. A sense of curiosity and of dissatisfaction that an issue is unresolved, or the facts unexplained, leads to a process of speculation whose conclusion is a hypothesis. A further visionary process connects the hypothesis with derivative predictions about the real world that can be looked for directly. Darwin's reputation as a scientist depends not only on the identification of natural selection as the effective process in evolution, but also on the extraordinary completeness of his analysis.