The first relates to the nature of Christianity. Put simply, Christianity is not invented fresh every Sunday but what is read, sung, preached and prayed in churches around the world stands within an established tradition; and church history allows us to understand how that tradition has come to take the form it has.
Take for example, the language of the Trinity with which typical believers will be familiar. Typically, Trinitarian language speaks of God as three persons, one substance. Such terminology is not specifically biblical, but the church has universally come to regard the terms as encapsulating important biblical concepts. Why has it done this? Why has the church come to use language which is not found in the Bible to express this important truth? Well, the answer is that the language is rooted in the creed approved by the church at the Council of Constantinople in 381; and the reasons why this creed has the form and terminology which it does have can only be fully appreciated when the various debates and discussions about what exactly the Bible taught about God’s being and nature have been examined. In other words, a knowledge of church history can help us to understand why things which in themselves seem perhaps a little pedantic, or obscure, are actually very important elements of the faith of anyone who claims to take the Bible seriously….
A second important reason for studying church history is the perspective it gives on the present day church. One of the amazing things I discovered when I moved to the United States was that I not only had a perspective on American life which made it easier for me, as an outsider, to see distinctive elements of the culture, but that I also came to have a better grasp on the British culture I had left behind. Living in America, I suddenly came to realise that things with which I had grown up, and which I thought were simply universal aspects of human civilisation, such as decent cups of tea and commercial-free television, were actually distinctive parts of British culture and not aspects of nature after all. As the goldfish cannot sense the water in which it swims, so we all swim unknowingly in our own cultural waters; it is only as we move out of our own cultural comfort zone that we come to learn such things.
Studying history is thus like emigration or extended foreign travel, only cheaper and generally less inconvenient. It gives the student the opportunity to visit another time, another place, another culture; and in so doing the student (hopefully0 becomes more aware of how the particulars of geographical and chronological location come to shape and influence the way people think. Thus at a time when ‘contextualisation’ is a popular contemporary cliche and shibboleth, history should really be coming into its own: study of context is, after all, something that historians have done for centuries. Indeed far from being the cutting-edge activity that so many assume it to be, ‘contextualisation’ is taken for granted by historians and scarcely thought worthy of special comment.
Carl Trueman, “The Trials of Church History” in The Trials of Theology, 133-135.