What follows here is a bit of material I might use in introducing the study of Christian history. . . .
What are some reasons for a Christian studying the history of the church? Why are we doing this? In response to that sort of question, I want to offer two ideas. My hope is that these two concepts can frame and set the tone for everything that follows.
1. The first point is general: We study Christian history because in the same way that memory is vital to personal identity, knowing a shared history is vital to group identity. If a movement is going to remain vibrant, then the people within that movement must know the basics of their history. Along this line, British historian John Tosh writes that no society or movement "can sustain an identity or a common sense of purpose without 'social memory' -- that is, an agreed picture of a shared past, which in most cases will be positive, if not inspiring." Knowledge of a shared past is basic to identity, and so the church should know its history. A good bit of literature stands behind this view. If someone is looking for scriptural support for this idea, consider the fact that many of the momentous sermons in the Bible include an historical prologue. So, whether it's Moses or Joshua or Samuel speaking to the ancient Israelites, or it's the Apostles preaching in the Book of Acts, many of these sermons begin with the history of the people of God.
2. The second point is directly and distinctively Christian: We study Christian history because many of the episodes teach us lessons and offer examples of people who exhibited true faith. People who are living the Christian life need examples of people who have been "joyful in hope, patient in affliction, and faithful in prayer" (Romans 12:12). We often see and hear that very thing whenever we delve into the history of the church. Which is to say that the study of Christian history can have a devotional quality to it, and be spiritually rewarding.
 John Tosh, Historians on History, 2nd ed. (Harlow, England: Pearson Educational Limited, 2009), 6.