Paul McCartney’s next book, coming out this fall, is a reminder that the Beatles were not his only band.

(AP Photo, File)NEW YORK – When Joe Biden addresses the country for the first time as president, his inaugural speech is likely to echo calls for unity that predecessors have invoked since the first time George Washington was sworn in. Unity has since been a theme, and an anxiety, for many incoming presidents, who have faced economic and social crises and moments when the very future of the U.S. was in doubt. “Unity has always been an aspiration," says presidential historian Douglas Brinkley. But when we have domestic turmoil we use the word unity.”The United States was forged through compromise among factions that disagreed profoundly on slavery, regional influence and the relative powers of state and federal government. “A president often claims the country is ‘united’ behind a belief when it’s more wishful thinking than reality,” Widmer says.