Robert Caro's biographies of President Lyndon B. Johnson are exhaustive, thorough and unbiased accounts of a complicated man. He sheds light on the President's domestic achievements (The Civil Rights Act), while paying equal attention to his controversial efforts to push Americans deeper into the shroud of Vietnam. There is a truism that every eager biographer must live by: real life is a messy thing. It's more complex and impenetrable than we wish to believe. Since it doesn't begin with a simple hypothesis, it cannot end with a tidy conclusion. And art, for the biographer, must imitate real life. In the lesson below, biographer James Curtis reminds us of the biographer's ever-important role in writing. "It's not your job to try and make your subject lovable," he says, just as "it's not your job to make your subject a villain." The words "approve" and "disapprove" must be swept under the rug of your vernacular. Biographers can only strive to "illuminate through understanding." After all, our actions in life are points to be connected, not proven.

James Curtis is most recently the author of "Spencer Tracy: A Biography," tracing the actor's faith, family and famed career on screen.