Hey, I forgot for a while, partially because I knew it would be a big task to respond fully. Today I bit the bullet and got to work...
I was unsure how much context to do, and I've been meaning to try out my scanner/OCR software instead of manually typing stuff like this in, so I went a little overboard and scanned/converted the whole section this comes from (the quality of the OCR surprised me!), which is about an 8 page range. The title of the section is "Approximate sufficiency of existing documents for the recovery of the genuine text, notwithstanding the existence of some primitive corruptions", and spans paragraphs 361 to 370 in the book (pages 276 to 284). The quote you're interested in is from the beginning of paragraph 367, so you'll have to scroll down about half-way down the page:
pargarphs 361 to 370
Note the immediately precending sentence refers to paragraphs 85-92, which I've also scanned:
paragraphs 85-92
You don't have to read the whole thing to get the point of my response to your original question about the quote.
Note that the context of the whole section, especially the immediately previous sentence (the last sentence of paragraph 366) shows us that the corruptions being discussed here are "primitive" errors (as defined/discussed in paragraphs 85-92): errors that are in the "
extant documents", "most original of recorded readings, the parent of the rest" (from paragraph 365) - in other words, a "primitive corruption" is a corruption that they believe occurred sometime *after* the autographs, but before or at the earliest
extant parent (as determined by their methods) - i.e., not the "autograph" itself.
That is their definition of "primitive corruption". Since and the precise quote under discussion talks of "the precise point at which such corruptions came in", when the quote goes on to provide an example of speculation for that corruption being "due to the original writer", I really don't think "original writer" is refering to the writer of a the original autograph, but the writer who produced a post-autograph copy which is the predecessor/parent to the earliest extant document. Note in paragraph 85 he says "Even in a case in which it were possible to shew that the extant documents can be traced back to two
originals which diverged from the autograph itself without any intermediate common ancestor...", indicating that he sometimes uses the term "original" to refer to a lost, non-extant parent source of one or more existing documents, not the "autograph itself" since it is "diverged from the autograph itself".
See also the sentence immediately following the quote. The following sentence says "Except from extraneous sources, which here have no existence, it is never possible to know how many transcriptions intervened between the autograph and the latest common ancestor of all the elements in all extant documents; and a corruption affecting them all may evidently have originated at any link of that initial chain."
The whole of the book, and their approach to textual criticism, assumes a "corruption" is something that differs from what was originally written in the NT autographs. Their whole purpose for doing what they did was to minimize/eliminate these "corruptions" - i.e. restore the text to match exactly what was in the autographs. A "corruption" is a *textual difference* from the autographs, not an imperfection (of whatever sort) within the autographs themselves.
Brian