Sergei said: "There is great difference between using multiple personalities as a valid plotting device.
and making ALL central characters parts of one."
Dear Sergei,
Mathew Roth's reply to your statement reminded me that I also had meant to reply to your criticism of my theory.
Are the three main characters of Pale Fire really Gradus, Kinbote and Shade? I don't think most reader's of the poem/commentary would agree with this although it is the conclusion of the person who wrote the Index. But I think most of us if asked would say that Sybil, Hazel and Shade are the three main characters. So the fact that Shade has an alternate personality or two hardly causes the problem you described. In fact it makes a far richer and more interesting story to think that Shade and his wife's actual relationship is mirrored in that of Charles and Disa. I think so, anyway.
Carolyn