The inventor of a brilliant idea cannot tell whether it is right or wrong. Livio quotes the psychologist David Kahneman describing how theories are born: “We can’t live in a state of perpetual doubt, so we make up the best story possible and we live as if the story were true.” A theory that began as a wild guess ends as a firm belief. Humans need beliefs in order to live, and great scientists are no exception. Great scientists produce right theories and wrong theories, and believe in them with equal conviction.
Theories are guideposts for action but you also have to be willing to be wrong since all life is an experiment anyway.