"The Story of Christian Theology: Twenty Centuries of Tradition and Reform" by Roger E. Olson
Historical theology is an important part of the process of deciding who we are, what we believe, and consequently how we will behave. For confessional Protestants, the past is not absolutely definitive, since all theologies besides
God's revealed Word err, but its influence on our lives is inescapable. Much of what we teach and do in our churches and schools is determined by what our forefathers said and did centuries ago and what we believe about that past. Therefore, we must tell the truth about the past. This is historical theology's primary vocation.