I’ve talked a bit about how it’s okay to fix mistakes, in most circumstances. This series of proofreading posts deals with the finding of said mistakes.
The sages were well aware that when you copy a document, and then copy from the copy, and so on, mistakes are likely to creep in over time. This is why we have a rule that even one mistake in a Torah scroll renders the entire scroll invalid for use until the mistake is fixed – zero-tolerance is really the only policy you can have if you want to ensure that your document will be absolutely unchanged.
This, incidentally, is also why we have the rule about copying from a copy. The scribe simply isn’t allowed to write the scroll down from memory – he may have it more or less accurate, but in a culture where each letter has the status of being divinely dictated, even a variation of one letter can’t be accepted, and recall from memory might mean whole words or phrases were a little bit off.
Relatedly, the roles of scribe and editor were pretty much interchangeable throughout much of history, and in most other documents, the occasional variation here and there doesn’t matter much, or is even expected (for further reading on this subject, see for instance Scribal Culture and the Making of the Hebrew Bible). But the Torah’s integrity was, for rabbinic Judaism, a theological principle, and as such, deviation from the text could not be accepted.
So it is that when you write a sefer Torah, you have to proofread it extremely carefully.
You have to go through the scroll and check that each and every one of the 304,805 letters is there and has its proper form. Ambiguity in form can be a bit of a disaster, since it can turn one word into a completely different word rather easily.
More about that in parts 2 through 14, which I originally posted individually at Hatam Soferet (2, 3, 4, 5, 6, 6a, 7, 8, 9, 10, 11, 12, 13, 14) but won’t inflict upon Jewschool as a series.
More about all this next week.