Metzger's commentaries often utilize historical criticism and higher criticism, which attempt to explain the literary and historical origins of the Bible and the biblical canon. For instance, Metzger argues that the early church which assembled the New Testament did not consider divine inspiration to be a sufficient criterion for a book to be placed in the canon. Metzger says that the early church, saw it as very important that a work describing Jesus' life be written by a follower of or an eyewitness to Jesus, and considered other works such as The Shepherd of Hermas and the Epistles of Clement to be inspired but not canonical.