Dov Ospovat's book, originally published in 1981, has become generally accepted as one of the most influential books about Darwin published in recent years. Ospovat examines the period of 1838-1859, two decades preceding the publication of On the Origin of Species, in detail and shows that Darwin's views changed quite radically from initially believing that animals and plants were perfectly adapted to their environments, and that evolution only occurred when the environment changed, to believing that living things were not perfectly adapted, were in constant competition with each other, and hence were continually evolving. By placing Darwin within the other biological developments of the day, he is able to show that he was not the scientific recluse of popular myth. He also shows that there was a theological basis for much of Darwin's original 1838-1844 theory, and his later principle of divergence was influenced by his belief in evolutionary progress.