Brad Littlejohn offers this concise definition:
…but if we may attempt to capture it in a nutshell, we might describe it thus: the Mercersburg Theology was a distinctively American yet cosmopolitan nineteenth-century theology— catholic, sacramental, both modern and ancient, Romantic and Reformed. Its eclecticism and historical awareness in an age of rigid orthodoxies, its ecumenism in an age of confessional quarrels, its theological seriousness and lofty speculation in an
American landscape dominated by anti-intellectualism, set it apart from the crowd of competing American theologies.{Series Introduction}