What is the difference between 'Biblical' and 'Systematic' theology?

Short answer: D.A. Carson offered a concise comparison within a larger article on the connection between Biblical and other kinds of theologies. Quote:

BT is historical and organic; ST is relatively ahistorical and universal. Unlike BT, which is deeply committed to working inductively from the biblical text so that the text itself sets the agenda, ST may (legitimately) be at a second or third or fourth order removed from Scripture as it engages, say, philosophical and scientific questions that the biblical texts themselves do not directly raise. But ST is the most comprehensive of the various theological disciplines.

Exegesis and BT have an advantage over ST because the Bible aligns more immediately with their agendas. ST has an advantage over exegesis and BT because it drives hard toward holistic integration.

ST tends to be a little further removed from the biblical text than does BT, but ST is a little closer to cultural engagement. In some ways, BT is a kind of bridge-discipline between exegesis and ST because it overlaps with them, enabling them to hear each other a little better. In some ways, ST is a culminating discipline because it attempts to form and transform one’s worldview. BT is important today because the gospel is virtually incoherent unless people understand the Bible’s storyline. ST is important today because, rightly undertaken, it brings clarity and depth to our understanding of what the Bible is about.

We can hope that more theologians from one camp (like BT) are willing to cross over and try to do ST, like Michael Bird, a Biblical Theologian who in 2013 published an ST textbook for the benefit of his students: Evangelical Theology: A Biblical and Systematic Introduction.

Longer answer (more on Biblical Theology):

The community doing Biblical Theology has become more conscious of their distinctiveness vis-à-vis practitioners of Systematic Theology and also differentiates within themselves 5 different ways of doing Biblical Theology. The article summarizes the big ideas of each way, provides concise description, adds a nice graphic, and gives a Passover example to differentiate the the 5 ways. The 5 ways are discussed extensively in a 2012 book Understanding Biblical Theology - A Comparison of Theory and Practice by Edward W Klink III and Darian R. Lockett.

Quote from the article on Type 2 of doing Biblical Theology:

Big Ideas:

• Biblical theology is about creating a "Big Story" (sometimes called Redemptive History or Salvation History)
• Biblical theology focuses on the historical events that make up the text
• Biblical theology traces the themes that run through Scripture as they were progressively revealed through time

The second type is also strongly historical and is similarly framed by history and the task of the historian, but its primary category is redemptive history. One step removed from BT1, BT2 is concerned to establish a whole-Bible theology, but similar to BT1, BT2 demands that the whole-Bible connections be made with historical resources. What holds the Bible together is still history, but a “special history” that is derived by theological criteria. The Bible reveals a History of Redemption progressing in a chronological manner. The history of redemption is visible through tracing the major themes and overarching structural ideas (e.g., covenant, kingdom, and promise and fulfillment) as they develop along a sequential and historical timeline. The biblical “theology” is only accessible through the lens of God’s (historical) progressive revelation.

In this way biblical theology is theological primarily in the manner it defines and utilizes history and is supported by the various themes running through the biblical narrative that serve as the connecting fibers between the biblical parts, including the OT and NT. While the historical nature of BT2 is directly parallel to the work of the academy, the goal is a biblical theology for the church. For this reason BT2 is a strongly exegetical task with an eye to God’s unfolding purposes throughout the ages. Such a bifocal hermeneutic tends to bend between a “what it meant/what it means” hermeneutic of Scripture. This interconnected approach to biblical theology has developed into different strands rooted in different ecclesial and academic traditions.

Type 2 seems to be the most popular lately, shown how:

• In 2018 Zondervan published the NIV Biblical Theology Study Bible edited by D.A. Carson, having the tag line "Follow God's redemptive plan as it unfolds throughout scripture".
• The decade older and highly acclaimed 2008 ESV Study Bible has a similar stance, providing key article titled "God's Plan of Salvation" as well as providing "History of Salvation Summary" in the Introduction of each book of the Bible.
• In 2011 Zondervan published a church bible study package called The Story: The Bible as One Continuing Story of God and his People. A Baptist church I visited used the videos and the materials from that package for their sermon-series as well as Sunday School materials that run for almost the whole year.

How to practice Biblical Theology? In the 2018 NIV Biblical Theology Study Bible, D.A. Carson authors several articles:

• What is Biblical Theology: concise definition as well as providing links to 101 Books on Biblical Theology: An Annotated Bibliography and a Tim Keller article: The Story of the Bible: How the Good News about Jesus is Central
• The Bible and Theology: arguing how the "feedback loop" flow is a better way than the older "hermeneutical circle" flow to interface Exegesis to Historical theology, Systematic theology, and Pastoral theology
• A Biblical-Theological Overview of the Bible: discussing the 3 faces of the practice of Biblical Theology as well as the shape & significance of Salvation History

The following article was written by Donald Macleod, who is Professor of Systematic Theology at the Free Church of Scotland College in Edinburgh, Scotland. The article appeared in a communication I received from "Reformation 21" on October 5 of this year. I've been on their email list for awhile now, and their mini-monographs and book reviews are generally quite good. I think Macleod's article is a great overview of some of the differences between the two theologies, systematic and biblical.

"The most obvious difference between Biblical Theology and Systematic Theology is that while the former adopts a chronological approach, tracing the history of revelation, Systematic Theology treats the Bible as a finished product in which God has spoken his last word.

"But the two disciplines also differ in their fundamental premises. Biblical Theology finds its starting-point in the diversity and variety of Scripture; Systematic Theology presupposes its underlying unity.

"There can be no denying the variety. Not only were the scriptures written at 'sundry times': they were also written in 'diverse ways' (Heb. 1:1). This was partly a function of their long historical time-line. They were written over a period of at least a thousand years and some of the oral and written traditions which they used may well go back a good deal further. They inevitably reflect, then, a wide variety of social, cultural and political settings: and, corresponding to this, a wide variety of forms of revelation.

"The result is that instead of a Bible in monochrome we have a Bible of varied landscapes, myriad voices and ever-changing colour: a wide variety of literary genres, ranging from narrative to poetry to law to parables to highly didactic epistles and even to fables (Judges 9:8-15); and, even more important, a wide variety of individual authors each with his own experience, gifts, temperament, vocabulary, favourite concepts, unique style and unique life-setting.

"The task of Biblical Theology is to highlight the distinctiveness of the various contributions: for example, the contribution of each era, of each literary genre (including Wisdom and Apocalypse) and of each individual voice. Each contribution must be accepted on its own terms. No two voices and no two eras have the same priorities or the same preoccupations. No writer feels bound simply to repeat the phraseology and vocabulary of his predecessors: the apostles did not even feel bound to stick to the terminology of Jesus. None follows his example in calling himself 'the Son of Man', none gives 'the kingdom of God' the prominence it had in the Master's teaching, and even prolific writers like the Apostle Paul make little direct use of key Old Testament concepts such as the covenant. On the contrary, each biblical writer plays his own word-game, with the result that the way that one author uses a word is no guarantee that it will mean exactly the same thing when used by another. John alone calls Christ the Logos, Paul alone uses the antithesis of flesh and spirit, the Writer to the Hebrews alone refers to Christ as a priest, and James alone speaks of being justified by works.

"These variations are a tribute to the . . . inspiration [of] the Holy Spirit [which] neither suppressed nor overrode the human personalities of the authors. Instead, they delivered God's word through the ordinary processes of human composition (even to the extent, probably, of wrestling with writer's block and agonising over the question whether it was really wise in the circumstances to say this at all). Biblical Theology glories in these variations, and the preacher who is conversant with its approach will be careful to identify the precise message which this author and this text bears. He may even, on occasion, draw attention to its limitations, pointing out what it does not say, and making good the omission from later revelation.

Systematic Theology: the unity of Scripture

"The premise of Systematic Theology, on the other hand, is the unity of Scripture: what the Westminster Confession (1:5) calls 'the consent of all the parts'. This in turn rests on the premise that all Scripture was breathed out by God, and while he may breathe out variety he will not breathe out contradiction. Precisely because Scripture in its entirety is the word of God it is the revelation of one saving will and of one plan of salvation. Systematic Theology assumes this unity, takes the whole of divine revelation as its field, and seeks to collate all that God has told us so far, striving towards the point where it can say to the church, 'This is the whole counsel of God. This is what you are to preach.'

"Yet we must never forget the provisionality of what we have to say, because our grasp of divine revelation is always partial and always fallible, and therefore always open to revision. From this point of view Systematic Theologians will always operate with a degree of scepticism towards earlier formulations (and of course contemporary 'original' ones, including our own).

"But we also have to recognise, beyond this, that there remain, and will always remain on this side of the End, things which have not yet been revealed. The premise of all theology is that God knows himself, and his self-knowledge is, of course, exhaustive. He could not, however, impart the same exhaustive knowledge to us. Instead, what happens in revelation is that he shares with us a little of what he knows about himself: but only a little, partly because there are aspects of his being which are beyond our capacity, partly because there are things which he thinks it best should remain hidden for the present, and partly because revelation is in no hurry. Neither he nor we are short of days.

"Solomon recognised (2 Chronicles 6:18) that 'the heavens, even the highest heavens,' could not contain the glory of God; and he added, 'How much less this temple that I have built!'

"Nor, indeed, can the Scriptures themselves. How much less our creeds and theological formulations! There is a parallel here between Scripture and the extra-Calvinisticum: the doctrine that while the 'fullness of the godhead' dwelt in Christ bodily (sōmatikōs) it could not be confined within that body. He was present and active outside (Latin, extra) his human nature, filling heaven and earth, and actively upholding the universe by the word of his power (Heb. 1:30).

"The underlying principle here was that the finite cannot contain the infinite, and it applies equally to Scripture. While divine truth fills the Bible, it is not confined within the Bible. It is indeed true, in the oft-quoted words of John Robinson, that the Lord has fresh truth to break forth out of his holy word. But he also has fresh truth to add to his word: truth which is not contained in our current Scriptures, but which he will 'break forth' to us progressively throughout eternity. After all, 'No eye has seen, no ear has heard ...' (1 Cor. 2:9).

"Assuming, then the unity and (provisional) finality of Scripture, what does Systematic Theology talk about? The short answer is that it talks about exactly the same things as Biblical Theology.

"But surely not in exactly the same way?"

Biblical Theology studies the Bible focusing on how God progressively revealed truth in it. It looks at it in chronological order showing how each new text adds to the ones before, sometimes in obvious agreement, sometimes in seeming contradiction. For example, Biblical Theology is crucial to understand how Christians should relate to the Old Testament Law - that Jesus came to fulfil it, that the sacrificial system is a shadow of the cross, that its prophesies focus on Jesus.

Systematic Theology studies the Bible as a system of interconnecting doctrines from the perspective that God's revelation has been completed and the Bible contains all we need to know. It answers questions like "What does the Bible say about money?" or "What is God's nature?" Done well Systematic Theology needs to rely on Biblical Theology in order to come to the correct conclusions. Done poorly it takes Bible passages out of their progressively revealed context and treats them all equally.

Biblical and systematic theology are two different ways of studying the Bible. The main difference is what the theologies study.

Biblical theology is focused on studying a portion of the Bible and how that relates to the rest of the Bible. An example may be specifically studying a portion of Isaiah. The person studying may look back at what led up to one of Isaiah's prophecies and how that prophecy is fulfilled in Christ.

Systematic theology focuses on different topics and studies what the Bible says about that topic. An example here may be studying the attributes of God. A person studying the attributes would start by finding all the scripture which mentions the attributes of God. After having all the scriptural references, they could then build a doctrine based on that scripture.

These methods of theological study are complimentary. While biblical theology may give you insight into a specific portion of scripture, it may not be the best way of building a doctrine since it may not give you all that scripture says on a specific topic. On the other hand, systematic theology can give you a very detailed view on a topic, but that view can be enhanced by providing even more context to the specific scripture which discusses a view.