“The Private Memoirs and Confessions of a Justified Sinner” by James Hogg (post 4): Why does this novel have symptoms of multiple personality?

Since this novel never mentions “multiple personality” (or its synonym, in those days, “double consciousness”), and since most literary reviews of this novel don’t say that the protagonist has multiple personality, it is evident that the author did not intend to write a novel about multiple personality, per se.

Thus, this is one more novel with unacknowledged symptoms of multiple personality. And the question arises as to why these symptoms (see post 3) are in this novel.

My theory is that it reflects multiple personality trait in most fiction writers.