Note: This is an expanded and revised version of material I originally wrote in 1996. The original version of my notes on this passage has been taken up and used—sometimes without attribution—by various brethren on their web sites supporting the KJV. One site in particular has an extended compilation of various defenses of the passage, including mine, mingled together with no indication of the sources of the various portions. I don’t begrudge my brethren the use of this material since their intentions are good, but do want to point out my authorship of the following in my own defense to avoid the reader thinking I have plagiarized it from someone else. If you read it on some other website before you saw it here, the proprietor of that site probably either got it from me, got it from someone who had it from me, or just decided he or she would “borrow” from it!
The current critical consensus regarding the last twelve verses of this gospel is that they are a spurious addition, since they do not appear in Codex Aleph (Sinaiticus), Codex B (Vaticanus), and a few other manuscripts of lesser importance. That the conclusion drawn by scholars in this regard is utterly erroneous appears from the following:
Dean John William Burgon exhaustively studied the manuscript evidence on this in his Last Twelve Verses of the Gospel according to S. Mark in 1871 (reprint ed. available from The Bible for Today). Burgon goes through the statements of the critics of his day against these verses, and shows them to have been the result of shoddiness of scholarship; he evaluates the passage on stylistic grounds; he examines the church fathers and the manuscripts on this passage; he even examines the oldest manuscripts and finds that in Codex B, or Vaticanus, at this passage there appears after v. 8 "the only vacant column in the whole manuscript;--a blank space abundantly sufficient to contain the twelve verses which he nevertheless withheld." He draws the obvious conclusion that the scribe who prepared Vaticanus "was instructed to leave them out,--and he obeyed: but he prudently left a blank space in memoriam rei. Never was blank more intelligible! Never was silence more eloquent!" (p. 87; emphasis original here and afterwards).
Burgon also comments that verses show the same abrupt style as the rest of the gospel--e.g., at Mk. 1:9-20--which is another proof of the present passage's authenticity (op. cit., pp. 143ff). He further suggests compellingly that the omission may have occurred because a liturgical reading in the early church ended after verse 8, since lectionaries and New Testament mss. that were adapted for church use often would have markings indicating where readings for given days should begin and end. It would be easy for a scribe seeing the ancient indication for the end of a reading, the Gk. word telos (meaning "end"), at the end of v. 8 as denoting the conclusion of the gospel.
Many of the stylistic arguments of the critics against this passage are somewhat questionable, to put it mildly. For instance, at v. 14, James White considers the description of Jesus' actions (i.e., where Christ "upbraided" the apostles "with their unbelief and hardness of heart")--
"quite out of character, given the other accounts of Jesus' dealings with the disciples after the resurrection. It is so strong that at least one scribe felt it needed toning down and introduced the ninety-word interpolation preserved today by codex W" (King James Only Controversy, p. 257).
Such a statement as White's belies a misunderstanding of what would be in or out of character for Christ to say, given the "strong" statement recorded in Luke 24:25-26 . The tone of address in the Luke passage, "O fools, and slow of heart," certainly seems to corroborate the description in the present verse--and I am not the only one to spot an affinity, as the 26th edition of the Nestle-Aland Greek New Testament gives a cross reference at Mk. 16:14 to the verse in Luke!
So the codex W scribe's "toning down" (assuming, with White, that this was this particular scribe's doing) proves nothing but that he misunderstood the passage much the same way as Dr. White did. As a matter of fact, the codex W addition and the so-called "Shorter Ending of Mark" are better evidence for the authenticity of the "Longer Ending" (verses 9-20) than against it. Such embellishments as that of the codex W scribe point out the profound chasm between crude forgeries which bear no trace of the evangelist's style, and the sublime manner of the "Longer Ending," which, as we saw, does share stylistic features with the rest of Mark.
Here is the codex W interpolation after v. 14, as translated in the NRSV:
"And they excused themselves, saying, 'This age of lawlessness and unbelief is under Satan, who does not allow the truth and power of God to prevail over the unclean things of the spirits. Therefore reveal your righteousness now'--thus they spoke to Christ. And Christ replied to them, 'The term of years of Satan's power has been fulfilled, but other terrible things draw near. And for those who have sinned I was handed over to death, that they may return to the truth and sin no more, that they may inherit the spiritual and imperishable glory of righteousness that is in heaven.'"
It is plain that many of the brethren have not thought through the implications of what they believe about this chapter of scripture. Ryrie, for instance, notes that--
". . . If [verses 9-20] are not a part of the genuine text of Mark, the abrupt ending at verse 8 is probably because the original closing verses were lost. . . ."
In similar wise, the "Guide to the Ancient Manuscripts" by Philip W. Comfort (unpaginated appendix to Tyndale House's Eight Translation New Testament) asserts that "Scholars have demonstrated that these verses are narratively incongruous with 16:1-8 . . . . Undoubtedly, Mark wrote more or intended to write more; but of such we have no record. Since the two earliest MSS. conclude with verse 8, we should accept this testimony--until more light can be shed on this textual problem."
Consider well what these writers are implying--that God could not preserve His Word well enough to get us the complete text of Mark without a few verses falling off the papyrus at the end, or could not preserve the Evangelist long enough for the gospel to be completed!
Over a century prior to Ryrie and Comfort, Burgon gave perhaps the definitive response to such speculations as theirs: "We listen with astonishment; contenting ourselves with modestly suggesting that surely it will be time to conjecture why S. Mark's Gospel was left by its Divinely inspired Author in an unfinished state, when the fact has been established that it probably was so left" (p. 245). And anyone who attempts to "establish" such a "fact" and challenge Burgon's defense of this passage--as opposed to simply ignoring his work and parrotting the line of those who continue to dismiss it--will, in my view, have more than enough to do to mount a case equalling Burgon's in breadth of learning, strength of reasoning, and reverence toward the God Who inspires Scripture.
The current position on Mark 16:9-20 is, then, severely misinformed, and one may accept these verses in the KJV with full confidence.