Bourne was an essayist and critic most remembered today for his opposition to U.S. military involvement in Europe and his assertion that "war is the health of the state.".

Bourne is also recognized as one of the founders of American cultural radicalism, revered in turn by Marxists, antifascists, and the New Left. Through his writings, he debated issues that were cultural as well as political from a position he described as "below the battle," rejecting the either/or political options of his day in favor of a viewpoint that argued outside the terms set by the establishment.

In her new study of Bourne's political thought, Leslie Vaughan maintains that this position was not, as others have contended, a retreat from politics but rather a different form of political engagement, freed from the suppositions that impede genuine debate and democratic change. In reexamining Bourne's writings, Vaughan has located the roots of twentieth-century radical thought while repositioning Bourne at the center of debates about the nature and limits of American liberalism.