The question has three answers: Lincoln composed the letter; Hay composed it and Lincoln signed it, perhaps after touching it; or someone else in the office did. The third is a residual. Nicolay was ill in St Louis from 17 to 30 November, and the clerks Hay mentioned to Mrs Langford are recorded only as writing the bodies of ordinary letters. We give it about 5 percent and do not analyse it further.
Between the first two the evidence is documentary, and each item is weak. We set out the items with the weight we give each, as a likelihood ratio: a number saying how many times more likely the item would be if one man wrote the letter than if the other did (a ratio of 2.4 for Hay means the item is 2.4 times more likely under Hay's authorship). A reader who weighs an item differently can see what changes. The ratios are judgments. The starting point, the prior before any item is counted, is the practice of the office as the record shows it: Lincoln wrote the letters that mattered to him personally, and the two condolence letters that survive from his presidency, to the Ellsworths in 1861 and to Fanny McCullough in 1862, are in his hand, while Hay wrote most of the rest and was writing routine letters for him that same week. We start at 65 percent for Lincoln.
| Item | What it is | Ratio | Running probability, Lincoln against Hay |
|---|---|---|---|
| Starting point | The office's practice: a governor's request through the Secretary of War, for a letter of a kind Lincoln wrote himself, in a week when Hay was drafting the routine ones | — | 65 |
| Hay's reported claims | Three chains (Morley to Butler; Brownell to Ogden; Page to Lady Strafford to Jackson to Lucas), none first-hand, none written down before 1922, two triggered by framed copies of the letter, one carrying a checkable error; plus two anonymous ones | 2.4 for Hay | 44 |
| Hay to Chandler, 1904 | "The letter of Mr. Lincoln to Mrs. Bixby is genuine." Consistent with either reading; Hay was answering a question about the forged facsimile | 1.2 for Lincoln | 48 |
| Hay to Robert Lincoln | Hay "knew nothing whatever of the source of the printed copy" and had "never seen any draft or copy," reported by Robert in 1908 and 1917. A man who drafted the letter would have known its source. Hay could have chosen not to tell Lincoln's son | 2.2 for Lincoln | 67 |
| Silences | Nothing in Hay's diaries, letters, memoir essay or family; his co-edited edition of Lincoln's Complete Works (1894) prints the letter as Lincoln's with a note on "its evident sincerity"; Spender, who discussed it with Hay, could not trace the story to him | 1.4 for Lincoln | 74 |
| The scrapbooks | A clipping of the letter among Hay's own poems and reviews at Brown, and another at the Library of Congress beside four other Lincoln letters; the same books hold material Hay did not write | 1.5 for Hay | 66 |
| "Beguile" | A word Hay used at least thirty times and Lincoln never, in a register Lincoln's surviving writing hardly touches | 1.5 for Hay | 56 |
| Stylometry | Section 4: the confound-controlled methods disagree and cannot detect known Hay writing in Lincoln's voice | 1 | 56 |
| Result | Lincoln against Hay, 56 to 44. With the 5 percent held back for a third hand: Lincoln composed it, about 53 percent; Hay, about 42; someone else, about 5 | 56 |
With the stylometry set at a ratio of 1, the case for Hay rests on the reported claims and the scrapbook clippings, the case for Lincoln on the office's practice and on what Hay told Robert Lincoln, and the two are close to a balance.
| If you instead… | Lincoln % | Hay % |
|---|---|---|
| take the 2019 stylometry at face value (a ratio of 10 for Hay) | 11 | 84 |
| give the own-hand stylometry its most Lincoln-ward reading (3 for Lincoln) | 75 | 20 |
| believe Butler's account of Morley exactly (a ratio of 8 for Hay in place of 2.4) | 26 | 69 |
| discount every reported claim to nothing | 72 | 23 |
| read Hay's statements to Robert Lincoln as discretion, not information (ratio 1) | 35 | 60 |
| start from an even prior instead of 65 percent | 39 | 56 |
| start from 75 percent, on the strength of the two autograph condolences | 64 | 31 |
Each row changes one item and keeps the others; the residual 5 percent for a third hand is held fixed. The first row is where the debate stood after 2019; the second is what the stylometry would say if only the classifier and Delta results were kept.