D1 rarely

How did Yeivin determine that Rule D1 is not obeyed in manuscripts in which vocal shewa is rarely made explicit? There are two ways I can think of that he might have done this.

• One way is by applying a criteria of internal consistency. What I mean by that is the following.
  • If we assume that the “vocality” of a word’s shewa does not vary across verses,
  • but we see, in some particular manuscript, that the use of gaʿya in that word does vary across verses,
  • then we could say, for that word at least, that Rule D1 is not obeyed in that manuscript. And, of course, if we see this inconsistent use of gaʿya across many words in that manuscript, then we could say, for the manuscript as a whole, that Rule D1 is not obeyed.
• The other way is by applying a criteria of external consistency. What I mean by that is the following. Let’s say we have two manuscripts, a reference one like μA, in which vocal shewa is often made explicit, and one under scrutiny, in which that is not the case: usually only simple shewa is used.
  • If we assume that the “vocality” of a word’s shewa does not vary across these two manuscripts,
  • but we see that the manuscript under scrutiny lacks gaʿya where the reference has ḥaṭef,
  • then we could say, for that word at least, that Rule D1 is not obeyed in the manuscript under scrutiny.