Editor's Note: (John McWhorter teaches linguistics, American studies, philosophy and music history at Columbia University and is the author of "Words on the Move." The opinions expressed in this commentary are his own.)

(CNN) When President Donald Trump revealed that he doesn't know why the Civil War was fought, or at least figures it could have been averted by the kind of deal-making he supposedly excels at, it was revealing in ways beyond the ones easy to glean.

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The ignorance is, as usual, stunning for someone in the public spotlight. "People don't ask that question, but why was there the Civil War?" Trump asks rhetorically, which is like saying no one has bothered to study anatomy or physics.

Yet this sort of thing should no longer surprise us from this man. He doesn't read and lacks curiosity, but that's hardly rare among human beings. A college teacher friend of mine the other day noted that no one in his class could name who was president in the 1980s, nor, upon being told who it was, could they name his political party. People like this don't mysteriously develop an interest in civics after college. Sometimes they become president.

Then there's Trump's question: "Why could that one not have been worked out?" Of course this implies that the North should have cut ever more deals with the South to continue enslaving black people. But Trump either 1) doesn't know enough about the Civil War to know that (upon which, see above), or 2) doesn't think the slavery issue should have been a priority.

Upon which we have two more choices. One is that Trump has engaged the literature suggesting that slavery would have evaporated in the United States on its own accord because of economic reasons. Again, however, see above -- which means that Trump doesn't "get" race.

His take on the Civil War is reminiscent of Trent Lott's jolly surmise during a commemorative event for Strom Thurmond that it was too bad "Ol' Strom" never became president. Lott, unaware the nation would hear what he said, revealed himself as just not thinking of little things like the civil rights movement as a priority. Trump is similar -- but we knew that, too, and it won't change.

Trump's neonate perspective on the Civil War reveals more than Trump's lack of book smarts or interest in "the African-Americans." Rather, Trump's ignorance about something as fundamental to our nation's history as the Civil War marks a profound disconnection from anything but his mundane self. It is this that reveals him as tragically unfit for his office.

He might claim an interest in history, but it is only on the level of a gee-whiz hero worship of the colorful exploits of an alpha male ex-soldier like Andrew Jackson. This is ultimately a continuation of a little boy's fondness for the likes of Davy Crockett (which Trump may well have had). Trump misses, for example, that Jackson would likely have despised him for his origins, his wealth and his personal conduct.

Meanwhile, Trump's lack of interest in even the basic currents of what happened in the past shows a disconnection from information beyond the casual and immediate. Here is the president who refuses to engage long-form policy papers, prefers television to print, and Twitter to thought.

As we see from his angered bafflement at sustained questioning from a CBS interviewer about things like his wiretapping claims, Trump is unfamiliar with sequential, extended argument -- i.e. concentration. People who can't focus shouldn't run nations.

A leader ideally should not be an outright nerd: governing doesn't allow the time to nurture the geekly needs. However, an effective leader must harbor a certain concentration upon something, be about something. Even the low-key George Bush père, lacking "the vision thing," was about statecraft and governance. His son was about serving his God. Bill Clinton was about public service in a Kennedyite vein. Obama was about healing and compromise in the name of moving ahead.

All of those themes require concentration and planning. Trump, however, has concentrated upon nothing but enriching himself. He eagerly watches and blabs about the tinny procession of events and sound bites going by on his television screens, but is sustainedly interested in nothing. He has no concerns, other than a sense of America as a macrocosm of himself, which therefore must be defended at all costs. But he knows too little about, well, anything to understand that America is infinitely more complex than he is.

This shouldn't have happened. One hears that to point out things like this is smug, which suggests that the analysis is mistaken in some way. One wonders, though, just what the evidence is that Trump is capable of concentration. I guess we should remember that when it comes to the race question in the 19th century, at least Trump has acknowledged the great things that the magnificently long-lived Frederick Douglass has been up to.