John 12:37-41 reads:
Although [Jesus] had performed so many signs in their presence, they did not believe in him. This was to fulfill the word spoken by the prophet Isaiah:
"Lord, who has believed our message,
and to whom has the arm of the Lord been revealed?"
And so they could not believe, because Isaiah also said,
"He has blinded their eyes
and hardened their heart,
so that they might not look with their eyes,
and understand with their heart and turn—
and I would heal them."
Isaiah said this because he saw his glory and spoke about him. (NRSV)
My question is whether "this" includes both of the preceding quotes or only the second. The NRSV is quoted as one of the few translations that uses "this" rather than "these things" to translate the neuter plural ταῦτα, for reasons that are unclear to me.
Is there grammatical or exegetical warrant to include only the second citation as being related to the prophet Isaiah's vision of glory?
Background and disclosure of motivation
The impetus for and potential implications of this otherwise perhaps trivial question may as well be stated. This arose in my reading of an article in the IVP Dictionary of the Old Testament: Prophets article on "Isaiah, Book of", which argues that Isaiah is best understood, for hermeneutical reasons, as having developed over a period of several centuries. The author (H.G.M. Williamson, who is well-respected for his work on the authorship and redaction of Isaiah) goes on to say:
Those [NT references to "Isaiah"] may be perfectly well understood as a reference to the book, not the author. The only passage where the prophet himself is involved in action rather than as speaker or author in the argument is at John 12:41 ("Isaiah said this because he saw his glory and spoke about him" [NRSV]), and there the citation from Isaiah 6 poses no difficulty.
The "hardening" saying of verse 40 is, of course, (adapted) from Isaiah 6, as is the prophet's vision of Yhwh's glory; on the other hand, "who has believed...?" is a direct quote of (LXX) Isaiah 53:1 — Deutero-Isaiah as far as Williamson is concerned. I'm trying to piece together how he was thinking about this.