Start with immigration, and the idea that any president could or should engineer the mass expulsion of 11 million unauthorized immigrants. Not one candidate said that a 21st-century trail of tears, deploying railroad cars, federal troops and police dogs on a continental scale, cannot happen and would be morally obscene. Ben Carson said, “If anybody knows how to do that, that I would be willing to listen.” They accepted the need to “control our borders” with a 2,000-mile fence. Even Senator Marco Rubio of Florida, once an immigration moderate, endorsed the fence. Mr. Carson actually suggested two fences, for double security, with a road in between. Do these people have to be sent to the Rio Grande Valley to see how ludicrous a border fence — over mountains, vast deserts, remote valleys and private property — would be? And it won’t solve the problem they are railing against, which doesn’t exist anyway. Illegal immigration has fallen essentially to zero.

On foreign affairs, there was a lot of talk about not talking with bad people. Senator Ted Cruz of Texas said his first act would be to tear up the Iran deal, throwing the nuclear race back to the ayatollahs and rupturing global alliances — but making a point! Carly Fiorina said: “What I would do, immediately, is begin rebuilding the Sixth Fleet, I would begin rebuilding the missile defense program in Poland, I would conduct regular, aggressive military exercises in the Baltic States. I’d probably send a few thousand more troops into Germany. Vladimir Putin would get the message.”

We get the message, and it’s scary.

Jeb Bush spun a particularly repellent fantasy. Speaking reverently of his brother the president, he said, “He kept us safe,” and invoked the carnage of 9/11. Wait, what? Did he mean George W. Bush, who was warned about the threat that Al Qaeda would attack? Who then invaded a non sequitur country, Iraq, over a nonexistent threat?

When the A-Team got around to science and health, many of them promised to help Americans by killing the program that gives millions of them medical insurance. One candidate said he felt sure that vaccines had caused an autism “epidemic.” The two doctors on the dais did not seriously challenge that persistent, dangerous myth.

Let loose by the CNN moderators, the candidates spun their visions freely. Despite an abundance of serious issues to talk about, nobody offered solutions to problems like child poverty, police and gun violence, racial segregation, educational gaps, competition in a global economy and crumbling infrastructure. On looming disasters (the changing climate) and more immediate ones (a possible government shutdown over, of all things, Planned Parenthood), the debate offered no reassurance that grown-ups were at the table, or even in the neighborhood.