From an early age German physiologist Jacques Loeb (1859-1924) was interested in the question of whether or not free will existed. Rather than pursue his interests via a philosophical approach, Loeb used science to address his question. Using biological experiments on a wide range of specimens, including dogs, caterpillars, and marine animals, Loeb concluded that there was not free will. He believed that all animals, including people, operated mechanistically, as a result of physical and chemical reactions to stimuli. He took this position a step further by arguing that, once scientists understood the mechanics of biology, they could ultimately control development.

Born in Mayen, Germany, in 1859, Jacques Loeb, born Isaak Loeb, was the first of two sons born to Benedict and Barbara Isay Loeb. His father worked as an importer, but was very interested in science, literature, and collecting books. He was especially interested in 18th century French...