by Los Angeles Times commentator Doyle McManus, on line and in print November 11, 2015

I don’t really mind that Ben Carson thinks the pyramids in Egypt were used to store grain; that’s a folk belief that’s been around since the Middle Ages. At least he dismisses the theory that the pyramids were built by space aliens.

And I don’t really mind that Carson’s autobiography, by his own admission, isn’t precisely accurate on every detail. He still insists that he tried to kill a classmate with a knife, an unusual claim for a presidential candidate. But even if that story was an exaggeration, it’s harmless myth-making — a dramatization of how low the teenage Carson had sunk before God intervened to shape him up. Barack Obama’s autobiography used creative license to make him sound like a juvenile delinquent, too.

Here’s what I do mind: Even though Carson considers himself brilliant, he doesn’t seem to care much about the actual duties of a president. His speeches, interviews and books betray a shaky grasp of economic and foreign policy, to put it kindly. And when a candidate is tied for first place for the Republican nomination in most polls, that’s no laughing matter.

Case in point: His comments about the federal budget.

Carson has proposed turning the income tax into a 15% flat tax on rich and poor alike — a massive tax cut for the wealthy (and tax increase for the poor) that would reduce federal revenue by more than half a trillion dollars, according to most estimates.

But more than a year after he began running for president, the good doctor still hasn’t explained how he would fill the yawning budget gap his tax cut would produce.

Indeed, this week he appeared to make the problem worse. Previously, Carson said he would cut federal spending by 3% to 4% across the board (except for the military, which he would grow). Now he says the cuts would amount to only 2% or 3% — a more realistic target, but one that would only widen the deficit.

Where are the details? There aren’t any available; none of these plans has been reduced to paper. A Carson spokesman told me that the campaign hopes to release specific proposals by the end of the year.

I don’t envy Carson’s aides; the candidate often sounds confused.

“The lion’s share of the gross domestic output is consumed by the federal government,” he complains in his latest book, “A More Perfect Union.” Actually, no: Federal spending consumes about 20% of GDP while consumer spending takes the true lion’s share: almost 70%.

On the public radio show “Marketplace” last month, Carson was asked whether he would block an increase in the federal debt ceiling. “I would not sign an increased budget,” he replied. No, his interviewer clarified, the question was about debts already incurred, not future spending. Carson still seemed to think they were the same thing. “We’re not raising any spending limits, period,” he said.

His vagueness and apparent lack of understanding on those counts isn’t comical; it’s troubling. Next to Carson, Ronald Reagan was a detail-oriented policy wonk.

Economics isn’t his only blind spot.

In his book, Carson argues that federal judges shouldn’t be allowed to rule on the constitutionality of state ballot initiatives like California’s Proposition 8, which the Supreme Court overturned in 2013.

“Having a ballot referendum on an important issue is a farce if a federal judge can throw out the results,” he writes. He suggests, as a remedy to this problem, that Congress simply impeach any judge who “ignores the will of the people.” So much for the Constitution.

Carson thinks the U.S. military should be taking the lead in ground combat against Islamic State in Syria and Iraq. “I would commit everything to eliminating them [Islamic State] right now,” he said. That’s a controversial position, but a defensible one. Here’s where Carson goes off course: He argues that U.S. forces shouldn’t be bound by the laws of war.

“There is no such thing as a politically correct war,” he told Fox News. “If you’re going to have rules for war, you should just have a rule that says ‘no war.’ Other than that, we have to win.”

Carson is, by all accounts, a brilliant surgeon. He’s a splendid motivational speaker and an admirable philanthropist. But he’s not ready to be chief executive of the United States.

In his books, he often mentions incidents in which God intervened in his life. When he neglected to study at Yale, God showed him the answers on a chemistry exam. When he fell asleep while driving home one night, God spared his life. When he used new surgical techniques on children’s brains, God saved some of his patients. And when he was on a safari in Africa, God answered his prayer for plenty of photogenic wildlife.

Now that he’s running for president, Carson sounds as if he’s counting on divine intervention to pull him through again. There can be no doubt about the sincerity of Carson’s Christian faith or his belief in the power of prayer. But voters — even the most devout — deserve more earthly evidence that he’s up to the job.

doyle.mcmanus@latimes.com