Ernst Heinrich Haeckel, the German zoologist and monist philosopher, was born in Potsdam. He studied medicine and science at Würzburg, Berlin, and Vienna with such authorities as Johannes Müller, Rudolf Virchow, and R. A. Kölliker. After practicing medicine for a short time, he went to the University of Jena in 1862 to teach zoology.

Haeckel was the first noted German biologist to grant enthusiastic acceptance to organic evolution, and Charles Darwin gave him credit for propagating the theory of evolution in Germany. His views were the source of considerable controversy in biology, philosophy, and religion. He battled with his colleagues about their early hostility to Darwin's theory and their reluctance to include man and his consciousness in the evolutionary process. His dislike of the power of the church in social and political matters and his liberal opposition to Otto von...