What is Theology?

Rick Leeman
Stunning sunrise casting rays over the Italian Alps in Alleghe, Veneto, with lush greenery and rocky terrain.

Definition

Theology, in its most basic definition, is the study of God.  The word is derived from the Greek words Theos, meaning “God,” and Logos, meaning “words.”  Yet, when one begins to study theology, we see the term used in many different ways and attached to many different words (like systematic theology, Reformed theology, and Pauline theology). 

In this article, I would like to explain the different aspects of the study of theology by giving brief definitions and examples of theological areas of study.

Systematic Theology

Systematic theology can be defined as what the entire Bible says about a particular subject.  All the relevant biblical texts are brought together to give one theological explanation.

For example, a “systematic” definition of the Trinity would be “the God of the Bible is one God, who exists in three persons—Father, Son, and Spirit—who are distinct from one another, yet fully and equally God.”  We see from Isaiah 43:10 that there is one God, because God says, “Before me no god was formed, nor shall there be any after me.”

In John 1, it affirms that Jesus, the Son of God, is himself fully God.  “In the beginning was the Word, and the Word was with God, and the Word was God. […] And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth. […]  No one has seen God; the only (or, ‘only begotten’) God, who is at the Father’s side, has made him known.” 

The Holy Spirit, who is called the Spirit of God and the Spirit of Christ, is presented as equal to the Father and the Son (Matt. 28:19), is called “Lord” like the Father and the Son (1 Cor. 12:4-6), his presence means God’s presence (1 Cor. 3:16).

These theological truths are then put together and we are given a “systematic” definition of the Trinity.

Systematic theology can be broken down into particular subject areas as well.  Some examples of these would be: “theology proper,” which is the study of God and his attributes; Christology (the study of Christ); soteriology (the study of salvation); pneumatology (the study of the Holy Spirit); anthropology (the study of humanity); and ecclesiology (the study of the church). 

Biblical Theology

Biblical theology is a bit harder to define than systematic theology, and the word “biblical” is not being used to say that it is truthful or accurate (as opposed to unbiblical theology).  Biblical theology traces the development of a particular doctrine through each book of the Bible, as well as investigates how theology is developed in a particular part of the Bible or by a particular author.  If we could describe Systematic Theology as an entire building, Biblical Theology provides the building blocks, which can be observed independently from the entire structure and from the other blocks.

Let’s use the Holy Spirit as an example.  Biblical Theology looks at how the Holy Spirit is described in each book of the Bible, yet without trying to put everything together systematically. 

In Genesis 1, he is present at creation.  In Judges, he empowers judges like Gideon and Samson.  In Isaiah 11 and 61, he empowers the Messiah.  In John’s Gospel, the Holy Spirit is a “Helper” who will come after Jesus ascends to the Father.  In Acts, the Spirit empowers the early church.  The Apostle Paul describes the Spirit acting as a “guarantee” of our salvation because he “sealed us for the day of redemption” (Eph. 1:13; 4:30). 

Each of those building blocks are important to put together a systematic “pneumatology,” but they can be investigated by themselves.

Under the topic of Biblical Theology is also how theology is developed and presented in different parts of the Bible or by different authors.  There is Old Testament theology and New Testament theology.  There is a theology of the Pentateuch (Genesis through Deuteronomy, which are attributed to Moses).  There is a Pauline theology from Paul’s letters; a Lucian theology from Luke’s Gospel and Acts; and a Johannine theology from John’s Gospel, John’s three letters, and the Book of Revelation.

These “theologies” differ from each other, yet each one adds important building blocks to understanding the Bible and theology as a whole. 

Historical Theology

Historical theology describes the development and understanding of theology from the closing of the biblical canon (c. 100 AD) to the present day.  This includes the development of the historic creeds and confessions of faith, the various heretical teachings that developed (which the creeds condemned), the development of the various denominations and sects, and the theological contributions of important figures throughout church history.

For example, the doctrine of the Trinity was—and still is—a battleground for theological thought.  In the first few centuries of Christianity, essential teachings on the trinitarian nature of God and the divinity and humanity of Jesus had to be clarified and confirmed over and against heretical teaching that was running rampant.  The Nicene Creed (325 AD) clarified the church’s stance on the Trinity, and the Chalcedonian Creed (c. 451 AD) clarified the church’s stance on Jesus being both fully God and fully man. 

These were in response to early heretical movements denied the full divinity and humanity of Jesus.  A sect called the Arians said that there was a time when Jesus did not exist, meaning he was not equal to the God the Father.  Today, Jehovah’s Witnesses believe in the old Arian heresy that Jesus is a created being (while historic Christianity says that he is uncreated; see John 1:3 and Col. 1:15-20). 

An early heresy known as Docetism (from the Greek worm meaning “to seem”) said that Jesus was God, yet only “seemed” to be human.  He did not have an actual human body and therefore could not have died on the cross.  On the opposite end of the spectrum is the modern-day belief that Jesus was human, but not God.  They say he was a human teacher, whose disciples wrote fantastical claims about in the New Testament documents, but modern Christians scholars have fought to refute these claims.

Historical theology also shows us how certain theological schools of thought were developed over time, following certain trends and figures.  Catholic Theology was developed in the Middle Ages (5th to 15th century AD), and was met head on by the Protestant Reformation, beginning with Martin Luther hanging the 95 Theses in 1517. 

The Reformation gave way to many of the theological schools of thought that we interact with today: Lutheran, Reformed/Calvinistic (which is followed by the Presbyterian denominations today), Arminian (which is followed by the Wesleyan Methodists), as well as the anabaptist and Baptist movement, which became convinced of only baptizing believers rather than infants (or, in the case of the anabaptist, rebaptizing Christians who were baptized as infants).

Next Steps

The answer to the question, “What is theology?” may have been longer than expected.  There are so many areas of study that fall under the umbrella of “theology,” and all of them are important to growing in your knowledge of Christ: you need Systematic Theology (to know what the Bible says); you need Biblical Theology (to know how the Bible is put together); and you need Historical Theology (to know how we got here).

If you are just beginning your theological journey, here are a few books that I would recommend:

  • ESV Study Bible (Crossway)
    • Study Bibles are helpful because they give explanatory notes on many verses as well as cross references.  The ESV Study Bible also has many short articles about various theological topics to continue to whet your appetite.
  • Wayne Grudem, Systematic Theology, 2nd Ed. (Zondervan)
    • Grudem’s Systematic Theology is very accessible as an entry way into systematics, written clearly and pastorally, while dealing with opposing viewpoints in a charitable way. 
  • Gregg Allison, Historical Theology (Zondervan)
    • This is a companion book to Grudem’s Systematic Theology.  The chapters are in the same order, and it traces the development of the doctrine through history.
  • Short Studies in Biblical Theology Series (Crossway)
    • These little books offer a short treatment of theological topics, traced throughout Scripture.  Topics include marriage, covenant, Satan, and the Kingdom of God.