While discussing a diagnosis with a patient, Siddhartha Mukherjee realized that there were no easy answers to the question, “What is cancer?” Faced with his hesitation, Mukherjee decided to do something about it.

Over the next six years, Mukherjee wrote the influential, Pulitzer-winning The Emperor of All Maladies, a 4,000-year “biography” of cancer. He collaborated with Ken Burns on a six-hour documentary for PBS based on his book, updating the story with recent discoveries in oncology.

In his new TED Book, The Laws of Medicine, he examines the three principles that govern modern medicine -- and every profession that confronts uncertainty and wonder.