Editor's Note: Sean B. Carroll is the author of Brave Genius: A Scientist, a Philosopher, and Their Daring Adventures from the French Resistance to the Nobel Prize. Here, as part of Biographile's Lessons Learned month, a month of authors sharing lessons they've learned while writing their book, Carroll shares the maxim that defines his writing, as well as the lives of his subjects, Jacques Monod and Albert Camus.

When I started the research for my newest book, Brave Genius, a few years ago, I knew that I had some huge holes to fill. The story that I wanted to explore was about two main characters, the biologist Jacques Monod and the writer Albert Camus. Both men were in the Resistance during the German occupation of France, had ascended to prominent roles, later became friends, and each won the Nobel Prize in their respective fields. But that was about all I, or anybody else, knew about any relationship between these two great minds.

While an enormous amount had been written about Camus, none of that illuminated his friendship with Monod, and relatively little was known about other important episodes in Monod’s life.

How and where could I find sources that could tell me about Monod’s experiences and character? Monod died in 1976. I was painfully aware that in trying to find out details about events that took place sixty to seventy years ago, I might not be able to find living witnesses.

But I got lucky, incredibly lucky.

While the necessity of such luck might serve as a general “lesson learned” about writing, it is a trivial point. My more meaningful discovery was not merely what some eyewitnesses could tell me about key events in Monod’s life, but how two extraordinary women exemplified a rare quality shared with my more famous subjects: courage.

Geneviève Noufflard is a retired concert flutist living in Paris. But in 1944, she was Monod’s close assistant in the Resistance. After contacting her through a French colleague, I learned the scope of what that entailed. Operating mostly out of her elegant Left Bank home, she made daily rounds about Paris to help Monod orchestrate missions involved in gathering intelligence, conducting sabotage, and coordinating arms drops. It was very dangerous work, as the Gestapo had men and informants all over the city.

Why did she, as a young music student, take on such risks? Geneviève told me that once she sensed the battle for liberation was coming, she was determined to join a group involved in direct action against the Germans. Monod tried to talk her out of it, and warned her of the prospect of arrest, torture, and deportation, but she could not be dissuaded. Many operatives close to Geneviève and Monod were caught, but they managed to elude the authorities and wound up in the inner circle of the Resistance during the dramatic battle for the liberation of Paris.

How did this wartime experiences shape Monod? I was struggling to understand when I met Agnes Ullmann, a retired biochemist at the famed Pasteur Institute, and learned her incredible story. Agnes first met Monod in 1958, when she visited Paris from Budapest on a limited visa. She revealed to Monod that she was in a miserable situation in Hungary. She had been very active in the failed Hungarian Revolution in 1956, and her husband had been jailed.

Although Monod was immersed in the most intense creative period of his career, conducting the key work that would earn him the Nobel Prize, he stunned Agnes by offering to help her and her husband escape from Hungary. Two years and several aborted attempts later, Agnes and her husband risked twenty years in prison when they were smuggled into Austria in an operation that called upon techniques Monod learned in the Resistance.

A few months before he died, Monod received a letter from a fifteen-year-old boy asking him as “one of the greatest researchers in the world” what maxim guided his life. Despite illness and his duties as Director of the Pasteur Institute, Monod replied, “All I can tell you are the qualities that appear most important to me … I would reply without a doubt that they are: courage, as much moral as physical.”

Through Agnes and Geneviève’s stories, I was able to see that such courage bound Monod to Camus and many of the other most important people in his life. But only by meeting these brave women was I able to truly appreciate and grasp what they meant.

For all Lessons Learned articles, visit the archive here.