I suppose I've been interested in Abraham Lincoln for almost as long as I can remember. My first Lincoln book was the Classics Illustrated comic book version of the life of Lincoln, and with that, I was hooked.

Until the early 90s, when I was working on a project about the idea of free will in American philosophy. I knew that Lincoln had had something to say about "necessity" and "fatalism," and so I began writing him into the book. In fact, Lincoln took over. I wrote instead 'Abraham Lincoln: Redeemer President,' in 1999, and I've splitting rails with Mr. Lincoln ever since. If there's a twelve-step process for this somewhere, I haven't found it yet.

Abraham Lincoln would have been happy to have solved the slavery problem by compensation - in fact, drew up a gradual, compensated emancipation plan as early as November, 1861 - but no slaveholders were willing to go along with it.

Was all of Stephen A. Douglas's promotion of 'popular sovereignty' a plausible device for getting him elected president? With his death in June, 1861, any possible answer to that question went to Douglas's grave with him.

We still know so little about how the brain interacts with the body chemistry or, for that matter, whether we should be talking about the brain or the mind, that it would be perilous to hazard any guess about the way Abraham Lincoln's biological health may or may not have affected him. Of course, we don't have Lincoln on hand to ask him directly; but even if we did, we still might not be able to make sense of how all the parts worked together.

It's often said that leadership is the art of getting people to do what you want, and making them think it's what they want. This captures a lot of what Abraham Lincoln did.

It would be pleasant to believe that some of Lincoln's DNA is actively swimming around in somebody's soup, but all the evidence is against it. And of course, there's always the risk that what we might get would be more Robert Todd Lincoln than Abraham Lincoln.