He was a professor emeritus at the University of California, Santa Cruz.
Schaar was born in Montoursville, Pennsylvania, and raised on a farm in a Lutheran family.
He taught political theory at the University of California, Berkeley, where his theory colleagues included Sheldon Wolin, Norman Jacobson, Michael Rogin, and Hanna Pitkin.
His closest students included the late Wilson Carey McWilliams, Jeff Lustig, Douglas Lummis, Marge Frantz, J. Peter Euben, Frank Bardacke, Joshua Miller, and S. Paige Baty.
He was married to political theorist Hanna Pitkin, and together they resided in the Santa Cruz mountains.