Louis Pasteur is revered as one of the greatest scientists in history — the father of germ theory, the inventor of pasteurization, the creator of vaccines for rabies and anthrax. But when historians finally gained access to his private laboratory notebooks a century after his death, they discovered that Pasteur had sometimes misrepresented his methods, borrowed rivals’ techniques without credit, and conducted his famous public experiments under conditions he concealed from the world.

This episode examines both the genuine brilliance and the carefully hidden deceptions revealed by Pasteur’s secret diaries, exploring how the patron saint of microbiology was also a ruthless competitor who bent the truth when his reputation was at stake.

• Pasteur’s genuine breakthroughs in germ theory, fermentation, and pasteurization
• What his private notebooks revealed about the anthrax vaccine trial he staged publicly
• The rivalry with Robert Koch and the competitive pressures that drove Pasteur’s deceptions
• How the secret diaries complicate but don’t erase Pasteur’s monumental contributions