Of primary importance in discussing the development of the New Testament canon is determining precisely what constitutes a “canon.” Historically, three primary schools of thought have emerged concerning the definition of the term the “canon.” Theodor Zahn argued that, since many of the foundational books of the New Testament were regarded as authoritative and scriptural by the end of the first century (as seen by their quotation by Christians such as Ignatius of Antioch), the New Testament canon should be understood as established and collected rather early on in the history of the Church, perhaps by the early second century. A second perspective was that of the late great Adolph von Harnack, who took a more fluid view of canon creation. Arguing that while the texts included in the New Testament where written early on in the Christian tradition, they were not regarded as totally authoritative until several decades (or even centuries, depending on the book) later. A third school of thought, as evidenced by A. C. Sundberg, relies heavily upon the rigid definition of “canon” as an authoritative list of scriptural books.  Thus, while early second century Christians such as Ignatius may have viewed certain books as important and useful, Sundberg maintained that the term “canon” cannot be applied to the Christian New Testament until authoritative canonical lists appeared in the fourth century. 
Fortunately, more recent scholars have realized that Zahn, Harnack, and Sundberg’s respective definitions of “canon” cloud with semantics what is often really being asked by canonical studies: when did people start collecting and using the writings of the New Testament as authoritative? As Bruce Metzger wrote, there is a difference between a “list of authoritative books’ and an “authoritative list of books.” In this semantic debate, scholars cam to the realization that further terms needed to be used to clarify what type of “canon” was being discussed. The chief terms which are used today include “formal canon” (an authoritative list of books, such as Athanasius’ Festal Letter 39, to be noted next week) and “practical canon” (a list or group of authoritative books, such as those referenced by Clement of Rome in his First Letter to the Corinthians). Recent canonical studies thus deals with two distinct, though interconnected, facets: the development of the practically authoritative canon of scriptures and the development of the formalized list of authoritative books which has become the Christian New Testament. This series will next turn to questions surrounding the formation of the “practical canon” before noting the eventual formation of the “formal canon.”
 Theodore Zahn, Geschichte des neutestementlichen Kanons, Leipzig, 1888-1892. Cited: John Barton, Holy Writings, Sacred Text: The Canon in Early Christianity, Westminster John Knox Press, Louisville, 1997, 2-4.  Adolf Von Harnack, The Origin of the New Testament and the Most Important Consequences of the New Creation, London, 1925. Cited: John Barton, Holy Writings, Sacred Text: The Canon in Early Christianity, Westminster John Knox Press, Louisville, 1997, 4-8.  John Barton, Holy Writing, Sacred Text: The Canon in Early Christianity, Westminster John Know Press, Louisville, 1997, 9.  Ibid., 9.  Bruce M. Metzger, The Canon of the New Testament: It’s Origin, Development, and Significance, Clarendon Press, Oxford, 1992, 282.