Once upon a time, the people most committed to the gospel were the people most inclined to serisous theological thought. The deepest doctrines of Christianity, the ones that are not on the surface of the Scriptures but lie waiting in its depths, were quarried through disciplined theological meditation and patient discernment. It was not academics or aesthetes with too much time on their hands who did this work, but busy pastors, suffering martyrs, and bishops overseeing the evangelization of entire cities. As they preached and taught and suffered for the gospel, they worked out the logic of the revelation of the Trinity, the incarnation, and redemption. The more seriously they took the life-changing power of the good news, the more concentration they devoted to the details of sound doctrine.
In modern times, things have been different: we take for granted that there must be an absolute divide between vital Christian experience on the one hand and careful doctrinal theology on the other. To us, action and reflection seem mutually exclusive, especially when it comes to Christian faith. The last thing we would expect to find is gospel and theology flowing from the same passionate commitment. But in the long sweep of Christian history, that is how it has usually been, from the church fathers to the scholastics through the Reformers and Puritans. All of them recognized that simple, saving faith could and should be elaborated into the Trinitarianism of Niceaea and the incarnational theology of Chalcedon. It took the crafty liberal theologians of the nineteenth century to popularize the argument that central Christian doctrines were, in Adolf Harnack’s words, “a work of the Greek spirit on the soil of the gospel” and a betrayal of the simplicity of Jesus’ message. At that time, conservative theologians disagreed. One of the great ironies of modern theological history is that the heirs of those conservatives who opposed high liberalism have become the chief bearers of the Harnackian bias against doctrine. Whenever we assume that the best way to embrace the simple gospel is to eschew the difficulties of doctrine, Evangelicals are unconsciously adopting the position of their historic opponents and standing in contradiction to their own best interests. In doing so, they take themselves out of the very stream of power that made their movement possible in the first place: the gospel stream of doctrine and devotion that flows from the church fathers to the first fundamentalists. J.I. Packer once defined Evangelicalism as “fidelity to the doctrinal content of the gospel,” counseling Evangelicals not to bypass the “doctrinal content” in the rush to get to a gospel. Fidelity to the gospel requires us to recognize doctrinal content, and those who would preach the gospel must make use of the tools of theology.
Fred Sanders, Jesus in Trinitarian Perspective, p. 5-6