In my previous post I wrote about the importance of systematic theology, not just for our thinking but for our spiritual life. Doctrine is very practical, and it leads to devotion which is not only heart-filled but clear-headed. There are usually nine or ten divisions traditionally given to the topics within Christian theology. Here's my list, with notation of how practical and devotional I find these studies...
BIBLIOLOGY is the study of the doctrine of God's revelation. He has shown us his will, as well as his thoughts, heart, and plan for history. This is important because it lays the foundation of God's authority in my life. I can know truth, and reality, and what is authoritative and important in life, because God himself has revealed these things to us in the Scriptures.
THEOLOGY PROPER is the doctrine of God, who he is, and what we can know about him. He is not a force, not some-thing beyond good and evil, not fatalistic. He is a sovereign and infinitely good Being, whose attributes are the pattern into which I am being remade into the image of God. His trinitarian nature reveals God to be relational and is reflected in his work of salvation -- the Father planning and ordaining, the Son accomplishing, and the Holy Spirit applying salvation to my life. This is who we love and adore.
ANGELOLOGY is the doctrine of angels and demons. This is practical in that it reinforces to me that I live in a supernatural universe, and also will face spiritual opposition in my life as a believer. It's vitally important to know about this.
ANTHROPOLOGY is the doctrine of humanity and creation. What were we created to be and to do? What’s wrong with me (i.e., the fall)? How I relate to both the dignity and the depravity of fellow human beings is an important part of my walk with God.
CHRISTOLOGY is the study of the truths about Jesus Christ, his nature and his work. He is my Savior, and here I learn what kind of Savior he is. He is fully human and fully divine. His work upon the cross is completely sufficient for all my need. His resurrection is the first fruit of the new creation. I am now "in him", and my spiritual life flows out of my union with Christ.
SOTERIOLOGY is the study of salvation. What did Jesus accomplish, and how do I receive it? What does it mean to walk by faith and what is my assurance of eternal life? What can I expect God to do in this life, and the next? These are truths vital to my spiritual life today.
PNEUMATOLOGY is the doctrine of the Holy Spirit. Is he personal or impersonal? What did the Spirit come to do? What can I expect of life in the Spirit? Where does my power come from? If the goal of my life is to walk by the Spirit (Gal 5:16-25), then it's important for me to know about his mission, role, and purpose in my life today.
ECCLESIOLOGY concerns the biblical truths about the church. What's the purpose and calling of the church today, and why is it important for me to be connected to the "communion of saints"? What is the role of congregational meetings, preaching, and the ordinances, in my growth as a believer?
ESCHATOLOGY is the doctrine of last things, which includes the end of history and the eternal destiny of believers and unbelievers. These teachings give me hope for the future and assurance that God is guiding history for his glorious purposes. The truth of the final judgment gives urgency to our witness to others.
IN SUMMARY, true spirituality is founded upon the truth of God’s Word (Bibliology), as we pursue a real relationship with him (Theology Proper), being Christ-centered (Christology), living in a supernatural universe (Angelology), seeing the image of God being restored in man (Anthropology), by faith daily trusting Christ's finished work (Soteriology), in the power of the Spirit (Pneumatology), vitally connected to God’s work among his people (Ecclesiology), and filled with joyful hope for the future (Eschatology). See how practical that is?
WHAT TO STUDY. First and foremost, study God's word, using cross-references and a good Bible dictionary. The earliest "theologies" were the Apostles Creed, and later, the writings of Augustine and Aquinas. John Calvin provided the Protestant Reformation with the Institutes of the Christian Religion (1559). There are many good one-volume works by William Ames, Louis Berkhof, John Frame, Michael Horton, and Wayne Grudem. My current go-to multivolume reference is Herman Bavinck's Reformed Dogmatics. A good place to start would be in one of the following: Everyone's a Theologian (R. C. Sproul), The Wonderful Works of God (Herman Bavinck), or Knowing God (J. I. Packer).