Biologist and historian Michel Morange tackles a monumental figure, closely retracing his contributions and contextualizing them in family, society, and culture. Pasteur was a complicated man, aware of his own worth, and likely to downplay other scientists' contributions, but also a tireless worker. The twists and turns of his research are fascinating to follow and lead to genuine advances. Morange covers Pasteur's personal convictions, especially his controversial relationship with Christianity. Hostile to positivism, he was susceptible to spirituality while clearly distinguishing between science and religion. This reference work draws on primary sources, research notes, and correspondance.