“Something there is that doesn’t love a wall,” Robert Frost writes in “Mending Wall” – one of two Frost poems, the other being “The Tuft of Flowers,” that addresses the nature of human relationships. “That sends the frozen-ground-swell under it, and spills the upper boulders in the sun; and makes gaps even two can pass abreast.”

The poem ends with the neighbor telling the poet famously, “Good fences make good neighbors.”

Well, they certainly make resentful ones. This has been a week of walls, literal and metaphoric, courtesy of President Donald J. Trump. There is the actual, proposed wall between Mexico and the United States whose cost would be covered by a tariff on Mexican imports like avocados. (Oh, no, whither Cinco de Mayo?) To say that Mexico is not taking this well is the understatement of 10 lifetimes. El Presidente Enrique Peña Nieto – not exactly the most popular man south of the border – nonetheless got a boost at home after he cancelled his meeting with Trump, though the two have since spoken by phone. ...