It has been said that F. J. A. Hort, in constructing the text of the Westcott & Hort edition, simply looked for the readings of B and followed those.
This is just about precisely backward. Hort did not start from some anonymous text and then start looking for ways to correct it toward B. Rather, he started from B and then looked for places where it should be rejected. In other words, he used B as a "copy text."
It is curious to note that the copy text (also known as a proof text), one of the fundamental devices of most classical textual criticism, as well as of textual criticism of authors in the post-print era, doesn't even seem to be mentioned in most manuals of NT criticism. Simply put, the copy text is the starting point for an edition. An editor, after examining the various witnesses, picks a particular manuscript as the best source and then, in effect, collates against it looking for places where a better text presents itself. As G. Blakemore Evans puts it in the textual introduction to the Riverside Shakespeare, "an editor today, having chosen for what he considers sound reasons a particular copy-text, will adhere to that copy-text unless he sees substantial grounds for departing from it" (p. 37). This, we should note, does not mean slavishly following the copy text; it at most means following it when we have no other basis for decision, or alternately in adopting its orthography and other minor details when the texts disagree.
G. Thomas Tanselle gives an analogy in his paper "Editing without a Copy-Text": "The controlling images of these two approaches are those of initially full and initially empty sheets of paper. If one chooses a copy-text, then in effect one begins with filled sheets and proceeds to alter the text present on them; but if one has no copy-text, one begins with blank sheets, so to speak, and fills them by placing one word after another on them, drawing those readings from relevant documents (and, on occasion, from one's own mind)." Thus there has never really been an edition of the New Testament prepared entirely without a copy-text; even an editor who considered himself to be starting from scratch, like Lachmann or Hort, would work from an existing printed edition for pure convenience -- so, in a sense, the copy text for the printed New Testament is the manuscripts that Erasmus used as copy text: 2e, 2ap, and 1r. But with so many generations of editing in between, these copy texts by now have had almost no effect on the text, although perhaps some slight influence on orthography.
It should be noted that the use of a copy text does not conflict with using the genealogical method. W. W. Greg, who defined copy text editing as currently defined, considered the use of genealogy, as practiced by Lachmann and Housman, to be established and correct procedure. His use of the copy text was for precisely those things where genealogical method was of no use -- spelling, punctuation, and all those details for which New Testament editors frankly ignore the manuscripts and just go their own ways. (One of the purposes of copy text editing was to stop the practice of modernizing spelling and such in editions of medieval authors.)
The term "copy text" has been around for quite a long time; R. B. McKerrow started using it in 1904 in his edition of Nashe. Arguably, however, the meaning of the term changed somewhat after W. W. Greg published "The Rationale of the Copy-Text" in 1950, because Greg drew a distinction between "substantives" and "accidental" readings and variants. Greg warned against the "tyranny of the copy text" (a phrase he apparent took from Paul Maas), which amounts to following the copy text even when the weight of evidence (internal or external) argues strongly against it. Indeed, he argues that the copy text should be chosen primarily on the basis of the accidental features, not the main features. Substantives are the variants which clearly have genetic significance -- e.g. there is the passage in Luke 22:16, where Jesus will not eat the Passover, or eat it again. This variant affects the entire dating of the Passion; it is a substantive variant. But whether a verb takes a first or second aorist ending will probably depend more on the grammatical knowledge of a particular scribe than on what the author originally wrote. The distinction has been compared to the distinction between form and content.
So Greg would have us turn to texts that are closer to the author in time to serve as the copy text, even if they have been dramatically altered in substantives. If, for instance, the choice in the gospels were somehow to come down to, say, D versus 33, we should go with D, even though it is heavily edited and far from the original text, because it probably preserves the original orthography better than 33 -- if for no other reason than that it hasn't undergone the change from uncial script to minuscule. (I note that, of the edited Greek New Testament texts I've seen, the only one which seems to make any accommodation to this principle at all is Westcott and Hort's, and even they don't go very far. On the other hand, they did come pretty close to one principle of copy text editing: when they were simply not sure which reading was best, they printed the text of their chosen source -- in this case, B. The modernization of all New Testament texts is particularly interesting in light of Fredson Bowers's assertions, "any text that is modernized can never pretend to be scholarly, no matter at what audience it is aimed." Quoted in G. Thomas Tanselle, Textual Criticism Since Greg, p. 21 n. 21.)
To be sure, Greg's method assumed that each successive edition derived from a previous edition which was still extant, and that is not true of the New Testament. In the above example, D and 33 are independently derived from the archetype. This makes the value of a copy text much less, and makes it harder to choose -- but it doesn't make the idea entirely worthless. (G. Thomas Tanselle does admit that "Obviously the spelling and punctuation of texts many steps removed from their authors (such as those dealt with by classical and biblical scholars) have a different significance from those in autograph manuscripts or editions (or copies) derived directly from manuscripts" -- although this comment is buried in footnote 37 on page 79 of Textual Criticism since Greg: A Chronicle, 1950-1985.)
Greg meant copy text editing to be used only for "expediency," as an easy path to a relatively good text. Some others are less willing to follow this principle. In the most extreme case, copy text editing may mean simply adopting the text which is most typical of the tradition -- that is, the one which allows the editor to produce the shortest critical apparatus. This was the form used by Fredson Bowers in some of his later work (and, in a way, lies behind the tendency in the International Greek New Testament Project and others to use the Textus Receptus as a collating base: The base text is not considered to have any authority, but it is convenient.)
Erick Kelemen, Textual Criticism and Editing: An Introduction (Norton, 2009), p. 102, emphasizes the point that some textual critics forget: the copy text "provides the chief authority for the readings of the accidentals but not necessarily the substantives" -- in other words, for details such as spelling and orthography but not for major variants. Hort didn't follow B closely; a good editor will be open to good readings from any source. But the copy text is the starting point. It is followed unless there is a clear reason to do otherwise. So, for example, one would tend to follow the copy text spelling of various proper names, or on points of Attic versus non-Attic usage, or on inflected versus non-inflected Semitic names. And, of course, in the case of readings where the canons of criticism offer no clear point of decision, you follow the copy text. It gives you a fallback if you have no other grounds for decision.
Note that this is in strong contrast to most methods of Eclecticism. Eclectics generally don't start anywhere; they have to decide everything -- even such trivialities as spelling variations -- from the manuscripts or from some external reference. It's a lot of work for slight reward -- and it arguably produces a rather inconsistent text.
I find it ironic to note that my preferred method of textual criticism, which is strongly based on manuscripts and genealogy, is considered hopelessly conservative and rigid by almost all New Testament critics, who prefer a more eclectic edition. Yet to editors of early printed works, with their copy-texts and their best editions, I would be a wild-eyed radical because I restrict my use of a copy-text! I can't help but think that both schools could learn from the other -- and, very likely, end up at a compromise rather like mine.
G. Thomas Tanselle, Textual Criticism Since Greg: A Chronicle 1950-1985, p. 13, sums it up as follows: "In somewhat blunt language, Greg's theory amounts to this: it tells the editor what to do when he otherwise does not know what to do."
We should note that the Copy Text notion arose in situations with very few witnesses -- e.g Shakespeare, where there are never more than three independent witnesses, usually not more than two, and occasionally only one. However, the idea has been successful enough that it is now applied to texts with far larger numbers of witnesses -- e.g. Chaucer, where some passages have as many as 75 witnesses. There is no inherent reason why the method could not be applied to the NT as well.
And there is a situation for which the Copy Text idea is so natural that I frankly find it disturbing that it has not been used until now, and that is the Hebrew Bible. The tension is always between those who would follow the MT too closely, because it's the only Hebrew text we have, and those who treat it as just another witness. In fact it is just another witness, but it is a privileged witness because it is in Hebrew. The Hebrew Bible should be edited by copy text: pick a base manuscript (Aleppo Codex or Leningrad Codex or whatever), and follow its orthography and its text when the matter is uncertain -- but then use the Qumran scrolls, and the LXX, and the Syriac, and the Vulgate, just as Greg used his other witnesses.
Of course, if one is to choose a copy text, there is the question of which copy text. This is rendered much more complicated by the nature of New Testament witnesses: Most of the important ones, the papyri and uncials, lack accents, breathings, punctuation, and spaces between words. Should one adopt a copy text which includes these features (in which case it will be much more recent than what are usually considered the best witnesses), or choose a text with the best text apart from readers' aides? Or even choose one text for the text and another for the aids?
If you prefer the Byzantine text, it probably isn't an issue. Others will face a harder choice. Personally, I would incline to take the best text, while allowing for the possibility of a text with more reader aids.
On that basis, I would suggest the following:
Gospels: B. Or ๐75 where it exists, but consistency argues for using B throughout. There are no other real candidates. ℵ is mixed and rather badly copied, and every other copy except D has Byzantine mixture. (Of course, if you prefer the Byzantine text, you can have a copy manuscript -- probably E or perhaps ฮฉ.
Acts: Again, B. Although there are proportionally more good manuscripts, none can claim superiority over Vaticanus.
Paul: Now this one is complicated, as there are fully four reasonable candidates: ๐46, B, ℵ, and (improbable as it sounds to list a minuscule) 1739. Nonetheless, I would argue that 1739 is the best of the choices. The best texts -- at least in my opinion and that of Stephen C. Carlson; compare also Zuntz -- are ๐46, B, and 1739. But ๐46 is very incomplete, and also contains a much-too-high rate of scribal errors. B is better on this count, but it too is defective. Adopting 1739 gives us a very good text, complete, and supplied with accents and breathings. The other alternative, ℵ, will appeal primarily to those, such as the UBS committee, who believe in Alexandrian Uber Alles without noting that the quality of the different types changes from corpus to corpus.
Catholics: Here again we have several options: B, ๐72, ℵ, A, C, and 1739 are all possibilities. ๐72 is probably eliminated by its incompleteness and its errors plus its wild text of Jude. A is the head of the main branch of the Alexandrian text, but while that is the largest group, it does not appear the best. C would have a strong case if it were complete -- indeed, if it were complete, it would be my first choice -- but it's too fragmentary. Textually, ℵ stands almost alone; so does B, whereas 1739 heads a large group. Ultimately, I would say the choice comes down to B or 1739. I would incline very slightly toward B.
Apocalypse: Here again we have four choices: A, C, ℵ, or ๐47. The latter is eliminated by its fragmentary state. ℵ isn't a particularly good text. C may well be the best text, but it once again has too many lacunae. We must choose A almost by default.
Those who wish to examine a text built on the copy text concept, a PDF of a text of Philippians (with critical apparatus, introduction, and commentary on significant variants) is available here.
We should recall, however, that the copy text concept can be applied to more than just the text of the New Testament. An edition of one of the versions might well be founded on a particular copy text (and some have been -- e.g. the Hopkins-James edition "The Celtic Gospels," an attempt to recreate the early Vulgate texts used in the British Isles, is based on Codex Lichfeldensis). So we should probably enumerate points to be considered in choosing a copy text.
Let's give the last word to W. W. Greg, whose work on this topic is considered to have revolutionized textual criticism from the period around the invention of printing:
[W]hen, as may happen in the majority of cases, the claims of alternative readings appear evenly balanced, [the editor] will naturally retain the reading of the copy-text, this being the text which he has already decided is prima facie the more correct. The exact degree of confidence that an editor need feel before he decides to alter the copy-text will necessarily depend on his mental constitution, and it would, I think, be futile to attempt to defend it. I will only remark that it may properly depend to some extent upon the confidence with which he has made choice of the copy-text, and that a cautious editor when hesitating will give the copy-text the benefit of the doubt. (The Editorial Problem in Shakespeare, third edition, p. xxix.)