What follows in the book then is page after page of evidence that this third definition is not just useful, but also necessary in achieving a proper understanding of what the NT canon is. He puts it this way: “The ontological definition focuses on what the canon is in and of itself, namely the authoritative books that God gave his corporate church.” (40) He describes the definition this way: “On this definition, there would be a canon even in the first century, as soon as the New Testament books were written.” (40) He calls it the Ontological Definition of Canon. Kruger then adds a third definition to flesh out these definitions. The weakness is the phrase “believing community.” Who gets to decide what a proper believing community is and is not? The other weakness is the same as we find with the exclusive definition: Are we to conclude that God’s word is only canonical when it is received and then used by a believing community? Furthermore, can we only conclude that these books are canonical if and only if they are collected into lists? The strength of the functional definition is that when “believing communities” used these books they actually treated them as canonical. The weakness is that these canonical lists don’t exactly match each other. The strength of the exclusive definition is that, by the 300’s – 400’s we have lists that show us what is in the NT and what is out of the NT. Kruger lets us know that there are strengths and weaknesses to these definitions. The Functional Definition: We know that books are canonical when they are treated as canonical by believing communities.Athanasius’ Festal letter or the canon table in Claromontanus) The Exclusive Definition: We know what books are canonical when we have a list of books to work with (e.g.He starts out by giving the two basic definitions of canon, in use today: His intent is to tackle the question (and definition) of what canon itself is. Kruger has a different intent and purpose in writing this book. There are a number of very good books which cover the topic of the New Testament canon, letting us know which books of the NT are all agreed on (homolegoumena) and the ones that people at various times and for various reasons had questions about (antilegomena). Michael Kruger is a professor at and the president of Reformed Theological Seminary in Charlotte, North Carolina.