premise: Robert Lewis Dabney (March 5, 1820 – January 3, 1898) was an American Christian theologian, Southern Presbyterian pastor, Confederate States Army chaplain, and architect. He was also chief of staff and biographer to Stonewall Jackson. His biography of Jackson remains in print today.
hypothesis: Dabney wrote the biography of Jackson in 1899.
reason: It was impossible for him to write it in 1899 because he died in 1898. I don't think the AI caught his birth and death dates.