Robert Todd Lincoln --The vitals

[L Verge]

Unless something is written down in the subject's own handwriting, how can anyone truly determine the veracity of the statement or even the occasion upon which it supposedly occurred? Isn't that one of the great pitfalls of attempting to be a historian? If Francis Carpenter or Ward Hill Lamon had heard Lincoln say that to Mary, would they have been taken more seriously than Elizabeth Keckly?