It isn't as easy as you make it sound. No way it could be an honest mistake, for a scribe to add a verse to an epistle and then for the same scribe (or his accomplice) to add a reference to that fake verse in Tertullian's or Cyprian's document. Or the other way around. It totally strains credulity, unless one postulates a deliberate deception.
If the copy a copyist is copying contains an error, the error will get copied if the copyist copies it faithfully. It is only if the copyist has multiple copies to copy and some are different from one another that the copyist will be alerted to there being the possibility of there being an error. Once an error occurs it will get faithfully copied until it gets spotted as an error, when enough differing copies can be compared with what's been faithfully copied from the erronious ones. It would depend upon in what era the mistake started and then got subsequently copied, and which sequence of copies were affected, surely. Wouldn't that be self evident?
No, you're not understanding it. Read again what @Invictus wrote: He's saying someone added a verse to the Bible, and then someone else took that verse and fabricated a supporting statement in something from a church father. Now, slow down and think about that. How realistic is that scenario? And if it happened that way, how can it not be an attempt at deliberate deception? For crying out loud, the very definition of interpolation includes this: "an act of interpolating something or the state of being interpolated : the introduction or insertion of something spurious or foreign." (Merriam-Webster Dictionary) In case you don't know, "spurious" means falsified.
"It is a mistake, often made by educated persons who happen to have but little knowledge of historical theology, to suppose that Fundamentalism is a new and strange form of thought. It is nothing of the kind: it is the partial and uneducated survival of a theology which was once universally held by all Christians. How many were there, for instance, in Christian churches in the eighteenth century who doubted the infallible inspiration of all Scripture? A few, perhaps, but very few. No, the Fundamentalist may be wrong. I think that he is. But it is we who have departed from the tradition, not he, . . . The Bible and the corpus theologicum [body of theology] of the Church is on the Fundamentalist side" (Kirsopp Lake, The Religion of Yesterday and Tomorrow, 1925, pp. 61, 62). My, how thinking has changed in 97 years. In 1925, the word "fundamentalist" was associated with solid, historical theology. Nowadays, some Anglicans have made "fundamentalist" a dirty word. What changed? Not fundamentalism. The change has been within Anglicanism, regrettably. I think "Modernist" should be the dirty word, because it's Modernists who are dirtying up the churches. I shall be proud to wear your yellow "fundamentalist" star.
Fascinating topic about the textual differences. I really don't know much about the subject but does it really matter in the end of the day whether one uses a critical text, a TR text or a majority text? Whatever the base text other readings are, in most modern translations, made known in the footnotes and any doubts or disagreements on certain parts are openly acknowledged. In the end nothing is missed out and we can all know what the variants say and make our own minds up about them. It seems to me that Christians have always had questions about variants and used manuscripts with variants in - from what I understand Origen mentioned variants in his day, Eusebius mentions doubts over the longer ending of Mark, Erasmus used texts critically in his Greek New Testament and the KJV translators also critically examined readings and made choices in their final translation. In this sense there's nothing new in what the critical text scholars are doing, some of the decisions may be wrong but then they have preserved disputed readings in the footnotes so nothing is lost.
I am willing to accept that you fellows may have the right of it. Further reading has shown me that many of the quotes from Westcott's and Hort's correspondence are ambiguous and are not necessarily as damaging as is claimed by some. Their involvement in occult activities could be explained by their youth and inexperience, and they may very well have repented and moved on later in life. If there was any connection between them and the RCC, such that they were working to bring down the KJV and to drive Protestants to the RCC, it is entirely unprovable because the evidence is all circumstantial at best. That said, I am quite convinced that their confidence in Sinaiticus was misplaced and unwise, and this heavy reliance on Sinaiticus, coupled with Hort's antipathy for the Byzantine manuscripts, influenced their work output in a negative way. (I have posted in other threads the reasons to doubt the reliability of Sinaiticus; no need to duplicate.) I also remain convinced that references found in the early fathers' writings are valid, important evidence which should have been (and should be) given greater weight in determining the best possible translation, especially when it comes to a decision to delete words or verses. To relate a bit of my own background, I recall using a Thompson Chain Reference NIV Bible quite extensively in the late 1980s and early '90s. When I encountered footnotes indicating that some manuscripts do not include such-and-such, it created doubt in my mind as to the integrity of Scripture. You see, I was quite familiar with those footnoted words and verses from prior experience; I knew that they had been taught to me as valid parts of Scripture, and I knew that they were accepted as Scripture by the churches I'd attended. So when I came across these footnotes (or sometimes the words appeared only in the footnote area of this Bible), it planted the thought in my mind to doubt whether I could trust what I'd previously read or been taught. And if those footnoted parts were questionable, how could I be confident of the whole? What if future 'discoveries' were made that cast new doubts upon even more verses' authenticity? A well-grounded Christian's faith might not be shaken by a Bible version that casts a cloud of doubt upon bits and parts. But I would suggest that only a very small percentage of Christians are "well-grounded" in their faith. (For example, if Christians were asked upon what basis they thought Jesus would let them into heaven, I'm pretty sure the great majority would incorrectly respond, "because I'm a mostly good person," or, "because my good deeds have outweighed my bad deeds," or even, "because I am a member of X Church." In other words, most so-called 'believers' are trusting more in their own self-righteousness or in a denomination's authority than in Christ.) It concerns me that the typical church-goer could be led further into doubt and unbelief by seeing that the editors of their Bible version admit they aren't sure whether such-and-such should be included or not. That's why I'm not fully convinced that footnoting is the wisest way to handle things.
Surely though it is advantageous, (whatever a Bible reader's level of faith may be), to be provided with a version of the scriptures which is as close as possible to what is generally agreed would have been the original text of the original manuscripts, in as readable a form as possible. If everything else which is generally considered by scholars to be 'questionable' for reasons of the text being for various reasons 'iffy' is put in italics, numbered or footnoted in some way, the reader still has the information but is no longer fooled into thinking that EVERYTHING they read in a version that supposedly contains EVERYTHING, is equally as essential to their salvation as what they might read in a version which has noted, numbered or footnoted all the agreed dodgy bits that may have crept in later on which can't be removed completely because they just might be genuine and still are very probably 'inspired'. I was impressed with the honesty of my RSV with footnotes. There are whole swathes of text that there are no problems with whatever. It was what stimulated my curiosity to discover more about how scripture came into being, way back when I was still searching for salvation. The truth will always release us from ignorance. .
Those two can be at odds with each other. I had the experience of reading Romans in NRSV and struggling to follow it, then read it in the Good News and found it legible at last. But having read and understood it in the Good News I can now follow it much better in the NRSV. But there are also some really bad versions around; Mirror, Queen James, Passion. (From what hear. I haven't actually read any of those myself.)
Good News Bible is a paraphrase and fairly good at explaining difficult grammar, particularly in Paul's letters. The living Bible, another paraphrase, is slightly less good, it has an Evangelical 'bias', which though not actually polluting the text, does present it in a very 'Evangelical' way. (Others, like for instance the New World translation 'look backwards' on the text from a fixed theological/doctrinal position and make it come out in support of their own views. John 1:1 is an example of this. Just goes to show what a difference an 'a' makes. .