Gary Dorrien, the leading authority on American liberal theology, defines it in the first volume of his three-volume historical work:
Fundamentally it is the idea of a
genuine Christianity not based on external authority.
Liberal theology seeks to
reinterpret the symbols of Christianity in a way that creates a progressive religious alternative to atheistic rationalism and to theologies based on external authority.
Specifically, liberal theology is defined by
its openness to the verdicts of modern intellectual inquiry, especially the natural and social sciences;
its commitment to the authority of individual reason and experience;
its conception of Christianity as an ethical way of life;
its favoring of moral concepts of atonement; and
its commitment to make Christianity credible and socially relevant to modern people.
—Gary Dorrien, The Making of American Liberal Theology: Imagining Progressive Religion 1805-1900 (Louisville, KY: Westminster John Knox Press, 2001), xxiii.
HT: Kevin DeYoung