Let’s begin by laying down the definitions for all of the different orders of theology that are mentioned above. First we have biblical theology, according to Elwell, “Biblical theology sets forth the message of biblical books by author or other scheme of grouping.”Paul Enns in his handbook on theology clarifies biblical theology when he says, “In contrast to systematic theology, which draws its information about God from any and every source, biblical theology has a narrower focus, drawing its information from the Bible (and from historical information that expands or clarifies the historical events of the Bible).”
According to Elwell, “Historical theology traces the churches faith topically through the various eras of its history.” In Elwell there is no mention of philosophical theology, however there is the mention of practical theology which is the application of systematic theology to every aspect of life.There have been several references to systematic theology, but no definition; Elwell defines it like this, “Systematic theology incorporates the data of exegetical, biblical, and historical theology to construct a coherent representation of the Christian faith.”Enns takes it even farther when he says, “Systematic theology may be defined as the collecting, scientifically arranging, comparing, exhibiting, and defending of all facts from any and every source concerning God and His works.”Now that all of these different areas of theology have been defined it makes since to say that systematic theology is the gathering together of all the different forms of theology. Biblical theology builds upon Scripture, historical theology helped to build systematic theology of the centuries as certain doctrines have developed.
Personally systematic theology with a good mix of biblical/covenant theology are the most important to my current ministry and hopefully my future role as a pastor. Without systematic theology it is hard to explain the concepts of the trinity, sin, Christology, and etc. Then being a reformed Presbyterian, I believe in covenant theology and showing how they continued to build upon each other throughout Scripture. It is through those promises we can take comfort, and seek to live lives pleasing and wholly devoted unto God. As a pastor they will all be important; however when doing aspects of evangelism systematic theology will be king, allowing me to break down different doctrines found throughout Scripture and supported by history.
 Walter A Elwell, ed. Evangelical Dicitonary of Theology. (Grand Rapids: Baker Academic, 2001)1164.
Enns, Moody Handbook, 149.