He was not a doctor. He was admitted to the Academy of Medicine by a majority of exactly one vote, and once, after explaining to that same Academy where chicken cholera comes from, he was challenged to a duel by an eighty-year-old orthopedic surgeon who did not believe in germs and did not intend to start.

Louis Pasteur also saved more human lives than anyone else alive in his century.

The Invisible World follows him from a tanner's yard in the Jura to a crypt lined with gold mosaic, and argues that everything he did came out of a single stubborn conviction formed when he was twenty-five: that living things can be recognized because they refuse to match their own mirror image. That conviction gave him fermentation, the death of spontaneous generation, pasteurization, and the first vaccine ever manufactured to order. The same conviction made him deny enzymes, dismiss toxins, and reject killed vaccines, including the one his own assistants quietly used to rescue his greatest public triumph while a hundred and fifty spectators and a correspondent from London watched the sheep.

Here is a scientist who proved causes not by looking at them but by building them, and who then did the obvious thing with something he had built: he patented it. Long before anyone had heard of a patent on a living organism, Pasteur held one. He fought for priority the way other men fight over land, because priority was the only property he had.

Neither a saint's life nor a prosecution, this is the story of a difficult, brilliant, half-paralyzed man who reorganized the world's understanding of disease, made a fortune from spoiled beer, and died regretting that he had never gone back to his crystals.