Natural Theology: That which man may know about God by viewing the creation of God. (Psalm 19:1-5, Acts 14:17, and Romans 1:20) What can we know of God from nature? God is a God of order (Examine flowers and their symmetry, examine the fungus and it’s symmetry). God is a God of variety (The species, sunsets, human faces, etc.). God is a God of immenseness (The distance between the planets and the stars).
Revealed Theology: That which man may know about God by viewing the Scriptures. (1 Corinthians 2:10 shows that God has revealed to man. How much can we know from the Revelation of God? A great deal can be learned from His Revelation. I have been studying the Word for more than twenty-five years. I have only studied about 26 books of the Bible personally. When I reread those books, I learn even more about them and the God that revealed them.
Historical Theology: That which man believed to be knowledge of God in times past. This information may or may not be correct due to their limited time to study a particular topic.
One of the obvious doctrines that was previously held, but now is in decline, is “Creationism.” At one time there was no doubt that the Genesis account was true, yet today the inroads of evolution, theistic evolution, etc. have caused their damage, even in conservative circles.
Historical theology is seen in the fact that the canon of Scripture was set many years after the day of Pentecost. Also it can be seen in the discussions of Christ’s natures many years later.
Biblical Theology: That which may be known about God from the study of the progression of doctrine in the Scriptures. In other words — progressive revelation. (What did Adam know of God? What did Abraham know of God? Did they know about the Rapture? No. God revealed Himself more and more through history, however all that was needed, to know God, was revealed at each and every stage so none were less knowledgeable about what God required of them than any other person in history. (see Ryrie p 14 for more.)
Systematic Theology: That which may be known of God by collecting all Scriptures together on a given topic to show the teaching of the Bible on that topic.
Example: Concerning the inscription over Christ on the cross: Mark 15:26 states, “The King Of The Jews.” Luke 23:38 states, “This Is The King Of The Jews.” Matthew 27:37 states, “This Is Jesus, The King Of The Jews.”
John 19:19 states, “Jesus, Of Nazareth, The King Of The Jews.” It takes four verses to know exactly what the Bible says on the topic.
Systematic theology is a systematic study and collecting of all information concerning God while it is also a system of belief. All information is gathered and then assembled into a system which is structured in such a way that it allows for all Biblical facts to fit into the system. Each fact is an integrated part of the system. If a fact does not fit into the system, then the system must be reformed to allow the fact to fit. It has always amazed me that most Bible Colleges and Seminaries wait until the students second or third year to teach them the system into which all of their knowledge is to fit. It seems much wiser to give an overview of the system at the beginning so the student can begin, immediately, to fit their new knowledge into their belief system. It also allows them to begin to evaluate the system to be sure it is within the teaching of the Scriptures.
Practical theology: That which may be used of God in the lives of man by applying the truths of Scripture to their life. When I was first saved I knew the commandment, “Thou shalt not take the name of the Lord thy God in vain.” (Exodus 20:7) The knowledge did not translate into action. For a long time, this commandment had no affect on my language. Later in my life the Lord began to work in my life, and this was one of the first practical applications of theology that He brought my way.
There are also theologies which are called Biblical but contain false teaching. Do not trust a title — look at the contents. We will look at a number of these in the study of Future things. (Dominion theology, Kingdom theology, Reconstruction theology.)
There are also some other areas of theology today. Pastoral theology, Christian Education theology, and contemporary theology. These use the term in our current ecclesiastical circles, though they are not technically a part of Biblical theology.
 by Stanley L. Derickson. DERICKSON’S NOTES ON THEOLOGY: A STUDY BOOK IN THEOLOGY.