Most Christians understand the importance of context for properly interpreting Scripture. We realize that the books of Scripture were written thousands of years ago in cultures very different from ours and in languages we do not grow up speaking. Those things that were simply given everyday realities for the original human authors and their audiences are things we have to study and learn about. We know that if we are studying the Old Testament, we have to learn Hebrew and Aramaic (or trust the translators who learned those languages). We have to learn about Ancient Near Eastern history, geography, culture and practices in order to understand what the biblical authors are talking about. If we are studying the New Testament, we have to learn Greek. We have to learn about the first century world under the Roman Empire. All of this is simply part of the nature of grammatical-historical interpretation.
Context is also important if we are to properly understand Reformed theology. Reformed theology was a fruit of the 16th-century Protestant Reformation, and that Reformation took place in a particular historical and cultural context. The authors writing at the time wrote within a particular philosophical and theological context. Having a grasp of these various contexts is important for understanding Reformed theology. I want to briefly mention three such contexts: the historical, philosophical, and theological contexts.
Historical Context -- The Protestant Reformation did not occur one afternoon because a bunch of Roman Catholic monks got bored and decided to throw a party that got out of hand. The Protestant Reformation was the culmination of numerous historical events that reached back over the course of many centuries. Conflicts between the church and various political entities (imperial as well as more local) in addition to various conflicts among the political entities themselves played a role. Conflicts within the church itself resulting from corruption and numerous reforming attempts played a role. Cultural changes, including economic changes and technological changes, played a role. We can see the direct relevance of the historical context when, for example, we read Martin Luther's To the Christian Nobility of the German Nation or his Babylonian Captivity of the Church, two of the most important Protestant writings of the early Reformation. We can see the relevance when we read John Calvin's "Prefatory Address to King Francis I of France" at the beginning of his Institutes. That preface is important context for understanding the content of the Institutes.
In addition, many of the Reformed confessions address issues that assume specific historical conditions or that are responding to specific historical conditions. The clearest example of the impact of historical context on the content of Reformed theology can be seen in the difference between the original Westminster Confession of Faith and the American revision of the same Confession on the subject of the civil magistrate and the relation between church and state. We have to understand that historical context is important for understanding Reformed theology. If a believer desires to have a better grasp of Reformed theology, he or she should take some time to study the history of the 14th and 15th centuries - the two hundred years immediately preceding the Reformation and then study the history of the 16th and 17th centuries themselves. Theology does not exist in a historical vacuum.
Philosophical Context -- In order to understand the importance of the philosophical context of Reformed theology, it is necessary to remember the historical time-frame of the Reformation. The Protestant Reformation began in the early 16th-century with the work of Martin Luther. The first Latin edition of John Calvin's Institutes was published in 1536. The final Latin edition in 1559. The major writings of Reformed theologians such as Zwingli, Musculus, Vermigli, Bullinger, Beza, Zanchius, and Ursinus were published in the 16th century. All of the works of the Reformed scholastic theologians in the period of Early Orthodoxy and the majority of the works published in the period of High Orthodoxy were published before the end of the 17th century. This includes the works of Reformed theologians such as Polanus, Ames, Wollebius, Maccovius, Witsius, Turretin, and Mastricht. All of the major Reformed confessions and catechisms were also published in these two centuries. For example, the Tetrapolitan Confession (1530), the First Helvetic Confession (1536), the French Confession (1559), the Scots Confession (1560), the Belgic Confession (1561), the Heidelberg Catechism (1563), the Second Helvetic Confession (1566), the Canons of Dordt (1618-19), the Westminster Confession of Faith (1646), the Westminster Larger Catechism (1647), and the Westminster Shorter Catechism (1647) are written in the 16th century and the first half of the 17th century.
This is important because it means that the great theological works of the classical Reformed theologians and the Reformed confessions that they produced were all published in the last days of a pre-Enlightenment philosophical context. In other words, these theologians were writing before the Enlightenment's "turn to the subject." Remember that the so-called father of modern philosophy, René Descartes, was born in 1596, at the very end of the 16th century. His most significant philosophical works were not written until the late 1630s and early 1640s, well into the 17th century, and it took time for the influence of those works to be felt in the universities and among theologians. This does not mean that the pre-Enlightenment philosophical context was monolithic. It also does not mean that there were no philosophical precursors to what became modern philosophy. There were, for example, in the philosophy of nominalism as well as in the ancient Greek skepticism that was rediscovered during the Renaissance. What it does mean is that the philosophical presuppositions of classic Reformed theology have much more in common with the general philosophical presuppositions of medieval theologians than with anything in the post-Cartesian era. In general, they worked within a context that did not question the existence of an external world independent of human minds or our ability to have true knowledge of that world through the use of our God-given sensory and rational faculties. Furthermore, they worked within a philosophical context that, with some exceptions (e.g. nominalism), granted that things have real natures.
This general philosophical context of Reformed theology was gradually lost as Enlightenment views finally filtered down and began impacting the thinking of the theologians. It had a catastrophic impact on Reformed theology. As Richard Muller explains (using the phrase "Christian Aristotelianism" to describe pre-Enlightenment philosophy):
The decline of Protestant orthodoxy, then, coincides with the decline of the interrelated intellectual phenomena of scholastic method and Christian Aristotelianism. Rationalist philosophy was ultimately incapable of becoming a suitable ancilla and, instead, demanded that it and not theology be considered queen of the sciences. Without a philosophical structure to complement its doctrines and to cohere with its scholastic method, Protestant orthodoxy came to an end (Post-Reformation Reformed Dogmatics, Vol. 1, p. 84).
In other words, if you want to know why there are so many Reformed theological giants in the 16th and 17th centuries and comparatively few afterwards, a large part of it has to do with the later theologians adopting various forms of Enlightenment philosophy and rejecting the pre-Enlightenment philosophical context. When Reformed theology is adapted to Enlightenment philosophical presuppositions, it withers and dies.
Our philosophical presuppositions affect our understanding of the most basic principles of reality and knowledge. Most readers of Reformed theology today have grown up imbibing post-Enlightenment philosophical principles without even being aware of it because it's the very intellectual air we breathe. This easily leads to a misunderstanding of traditional Reformed doctrines if we read those doctrines through post-Enlightenment lenses. More seriously, many contemporary Reformed theologians have consciously or unconsciously adopted one version or another of post-Enlightenment philosophy. Post-Enlightenment philosophy has an enormous impact on our understanding of God, man, sin, everything. When a contemporary Reformed theologian who has adopted one form or another of post-Enlightenment philosophy also subscribes to a Reformed confession, all of which were written by theologians who thought within a pre-Enlightenment philosophical context, there will inevitably be internal conflict. The temptation to radically revise or reject the confessional teaching will be ever-present. Such radical revision and rejection of confessionally Reformed doctrine has already begun to occur. We see this most clearly in the writings of contemporary Reformed theologians who reject the doctrine of God taught in the Reformed confessions (e.g. WCF, ch. 2).
Theological Context -- If someone desires to study the theology of the Canons of Dordt, we generally understand that it’s necessary to have some grasp of the Arminian controversy and the theology of the Remonstrants because the Canons of Dordt are responding to the specific doctrines of the Remonstrants/Arminians. The same principle is true also of classic Reformed theology in general. Reformed theology is responding to and re-forming something that already existed – namely late medieval Roman Catholic theology. This assumed theological context can be seen throughout the writings of the early Reformed theologians and throughout our Reformed confessions. Over and over again, we see the Reformed theologians and the Reformed confessions responding to various specific Roman Catholic doctrines and practices. Sometimes they correct those doctrines and practices. Sometimes they completely reject those doctrines and practices. Unless we have some understanding of those Roman Catholic doctrines and practices, it can be very difficult to understand what our Reformed theologians and confessions are getting at.
The Reformed theologians of the 16th and 17th centuries understood the theology of late medieval Catholicism, and they could assume that most of their readers (other theologians and pastors) would have some understanding of it as well. Many, if not most, contemporary readers of Reformed theology do not have the same basic knowledge of Roman Catholic doctrine and practice that the early Reformed theologians and their readers had. They do not have the same grasp of the overarching ecclesio-sacerdotal-soteriological system of Roman Catholic theology. They may have heard isolated bits and pieces regarding things such as justification or the relation between Scripture and tradition, but most do not understand the all-encompassing nature of the entire Roman Catholic theological system and how each piece relates to all of the others. This puts contemporary readers of Reformed theology in something like the position of a reader of the Canons of Dordt who does not understand the Arminian theology to which those Canons are responding. We can get some understanding of Reformed theology without that knowledge, but without the theological context it is very easy for that limited understanding to slide into misunderstanding. How many Reformed Christians, for example, understand how significant Rome's understanding of Adam's pre-fall constitution and the relation of nature and grace at that point in time is for Rome's understanding of sin, and grace, and justification? That knowledge is an important context for understanding the Reformed theology of sin, grace, and justification.
Conclusion -- Classic Reformed theology did not fall out of the sky without any context. It was developed within real human history with real historical, cultural, political, philosophical, and theological contexts. We are five hundred years removed from those contexts. Our 21st century historical, philosophical, and theological context is very different from that of the 16th and 17th centuries. If we are not aware that there are differences, it can be very easy to read our contemporary context back into the writings of those centuries. If we are aware that there are differences but remain ignorant of the 16th and 17th century contexts, we can easily miss the true import of some of their teachings. In short, the same kind of effort that we put into learning the context of the biblical writings ought to be put into learning the context of classical Reformed theology.