I’ve got a high school diploma and a whole semester of technical college under my belt and I’m going to crudely explain Systematic, Biblical, and Historical Theology.
This is the most common way to study theology. Basically, all of the information in Scripture is put into different categories and these categories are taught ‘systematically’ (hence the name). The main idea behind systematic theology is make clear what Scripture as a whole teaches about a particular doctrine or idea.
Biblical Theology is a less common way to look at theology, but it is still important nonetheless. Personally, this is my favorite way to look at theology so it’s possible that I could be a little biased. Biblical Theology seeks to looks at the narrative of Scripture on a particular topic. Because of this, Biblical Theology will, at times, overlap with Systematic Theology. The main difference is how the ideas are presented. While Systematic Theology looks at what Scripture as a whole says about an idea or a doctrine, Biblical Theology will often look to see how that doctrine or idea has evolved from Genesis to Revelation.
Recommended: What is Biblical Theology? – James Hamilton
Finally, we come to the seemingly most ignored of the three methods, Historical Theology. While Historical Theology does look at what Scripture says about a particular doctrine or idea, it also goes outside the bounds of Scripture and looks at how a particular doctrine or idea has been taught and examined throughout church history leading up to the present day.
An article on Got Questions accurately summed it up in this way:
“Like any area of theology, historical theology is also sometimes used by liberal scholars and non-Christians to cast doubt upon or attack the essential doctrines of the Christian faith as simply being the concoctions of men instead of the divinely revealed biblical truth that they really are. One example of this is in the discussion of the triune nature of God. The historical theologian will study and trace the development of this doctrine throughout church history knowing that this truth is clearly revealed in Scripture, yet throughout church history there have been times when the doctrine came under attack and thus it was necessary for the church to define and defend the doctrine. The truth of the doctrine comes directly from Scripture; however, the church’s understanding and proclamation of the doctrine has been clarified over the years, often in times when the nature of God had come under attack by those “savage wolves” that Paul warned would come.”
The article goes on to say:
“Historical theology, when correctly understood and applied, does not diminish the authority or sufficiency of Scripture. Scripture alone is the standard in all matters of faith and practice. It alone is inspired and inerrant. Scripture alone is our authority and guide, but historical theology can help us understand the many dangers of some “new teaching” or novel interpretation of Scripture. With over 2,000 years of church history and thousands if not millions of Christians preceding us, shouldn’t we be automatically wary of someone who claims to have a “new explanation” or interpretation of Scripture?”
Recommended: Historical Theology – Alister McGrath
Systematic theology asks, “What does the Bible as a whole say about x?”
Biblical theology asks, “How did the writers of Scripture understand the idea of x, and how did this concept evolve from Genesis to Revelation?”
Historical theology asks, “What can we learn about x from the time of the Bible all the way up to our present day?”
None of these methods are perfect. They all have their pros and cons. Glean from all three methods of studying and don’t just get stuck in one mode because you’ll create a theological blindside for yourself.
Like I said earlier, this is a crude explanation. If I left something out or said something incorrectly (and I probably did), let me know about it in the comments.