Darwin was the most important naturalist of the eighteenth century. Trained as a physician at Cambridge and Edinburgh, Darwin became famous for his radical opinions. Later he was a member of the Birmingham Lunar Society, which included Joseph Priestley, also known for his radicalism.. There he was exposed to the work of David Hartley, whose theory of psychological association proved influential in his own work.
Darwin's biological writings spelled out a theory of evolution, although his notion of the evolution of species closely anticipated not that of his grandson, but of Charles Darwin's most formidable rival, Lamarck. Basing his work not on systematic research but simple observation, and drawing on theories of materialism, he presented a simple model of evolution which was quickly superseded by the more sophisticated nineteenth-century biologists.
His works include The Botanic Garden (1789-1791) and Zoonomia (1794-1796).