It is urgent for Americans to think and speak clearly about President Trump’s inability to do either. This seems to be not a mere disinclination but a disability. It is not merely the result of intellectual sloth but of an untrained mind bereft of information and married to stratospheric self-confidence.

In February, acknowledging Black History Month, Trump said that “Frederick Douglass is an example of somebody who’s done an amazing job and is getting recognized more and more, I notice.” Because Trump is syntactically challenged, it was possible and tempting to see this not as a historical howler about a man who died 122 years ago, but as just another of Trump’s verbal fender benders, this one involving verb tenses.

Now, however, he has instructed us that Andrew Jackson was angry…