Purposes of Miracles
The majority of New Testament scholars do not think this verse or the last twelve verses of Marks Gospel were written by Mark himself. They think that the original ending to Marks Gospel was lost and that these verses were added later by someone other than Mark. Nevertheless, these last twelve verses were written very early in the history of the church, for they are found in several manuscripts of Tatians Diatessaron (A.D. 170). They were also quoted by Irenaeus (who died in A.D. 202) and Tertullian (who died in A.D. 220). At the very least, therefore, these verses reflect what the early church thought about the purposes of miracles, even if these verses are not considered part of the original Scriptures.