We must first define Theological Liberalism in order to correctly understand Theological Conservatism.
It is unrealistic to refer to anything as theologically liberal before Friedrich Schleiermacher, the early 19th century “father of liberal theology.” Schleiermacher was certainly influenced by previous and contemporary thinkers in philosophy and theology, but he almost single handedly created “liberal theology.” On this most historians agree. (Before Schleiermacher there were “free thinkers” and deists and unitarians but not liberals per se.)
Theological Liberalism first appeared as a movement with German Lutheran theologian Albrecht Ritschl and his followers in the late 19th century. This was born out of German Rationalism. Schleiermacher introduced into the stream of Christian theology a revolution in theological methodology that believed it was necessary to adjust traditional Christianity to the culture of the Enlightenment–what we call “modernism.”
Schleiermacher redefined Christianity as primarily about human experience. That is, as he put it, doctrines are nothing more than attempts to bring human experiences of God (God-consciousness) to theology. Schleiermacher placed universal God-consciousness at the center of religion and Christ’s God-consciousness communicated to the church at the center of Christianity. All doctrines and all teachings of Scripture became malleable, changeable, in the light of human experience. This, or course, reflected the popular philosophy of Immanuel Kant.
Delwin Brown (a convert to liberal theology from evangelicalism) in his dialogue with Clark Pinnock in Theological Crossfire: An Evangelical/Liberal Dialogue, Brown asks the crucial question of modern theology: “When the consensus of the best contemporary minds differs markedly from the most precious teachings of the past, which do we follow? To which do we give primary allegiance, the past or the present?” Brown rightly gives the evangelical answer: “We ought to listen to the hypotheses of the present and take from them what we can, but ultimately the truth has been given to us in the past, particularly in Jesus, and the acceptance of that is our ultimate obligation.
Everything the contemporary world might say must be judged by its conformity to biblical revelation.”
And that last sentence is your definition of Theological Conservatism.