Most people seem to believe that the “ad hominem” argument is America’s most appealing fallacy. It’s frequently cited and gives people a chance to show off the only Latin phrase they know. It’s an argument against a position or opinion that attacks the person, not his reasoning or evidence. For example: “Adolf Hitler’s racial theories were a crock of cracked pot shards because he was a vegetarian who committed genocide. This, we note is not a false statement. It is a true statement but it is not a logical refutation of the man’s deranged ideas.

It proposes that “post hoc ergo propter hoc” (literally, “after this therefore because of this”) is far more popular, even though few people have heard its name. It implies that because one thing occurred after another, it must have occurred as a result of it. Reasoning thus, a simpleton might conclude that a cat must cause the dog that chases it. Moving up several cognitive notches this fallacy produces the very common error of confusing correlation with causation. This is so common that I suspect I must have committed it myself, and more than once. (NB: “suspect”—I admit nothing…)

Here’s an example which should make the post hoc, propter hoc problem clearer. The U.S. Dept. of Agriculture, Economic Research Service has compiled accurate figures for American margarine consumption between 2000 and 2009. The U.S. National Center for Health Services, National Vital Statistics Reports on Births, Marriages, Divorces and Deaths in Maine during the same period with the same accuracy. Plot the margarine consumption and Maine’s divorce rates together on the same graph and you will find a 98.9% correlation. If you were unaware of the logical fallacy (or were otherwise dim-witted) you might conclude that a reduction in margarine production would reduce the divorce rate in our state.

Tyler Vigen’s “Spurious Correlations,” loaned to me by my younger sister, is full of similar graphs. I must emphasize that the correlations are not really spurious. It’s the supposed conclusions that are spurious.

We have suddenly been seeing a national epidemic of this fallacy. President Trump, the most verbose if not the most eloquent American president of recent memory, gassing away with his usual volubility during last year’s midterm elections warned that America was under attack by immigrants heading for our southern borders. “You look at what is marching up, that is an invasion!” he declared at one rally. “That is an invasion!” Nine months later a “suspect” who killed 20 people at an El Paso Walmart was found to have written a manifesto declaring that his attack was a response “to the Hispanic invasion of Texas.” It’s true that his manifesto declared that his invasion fears predated Trump’s assertion, but a New York Times analysis argues that “if Mr. Trump did not originally inspire the gunman, he brought into the mainstream polarizing ideas and people once consigned to the fringes of American society.”

The Times’s “analysis” echoes the condemnations trumpeted by politicians desperate for the Democratic Party’s presidential nomination. The echoing will continue at least until the 2020 general election and may continue with diminishing fervor thereafter. We would commit the post hoc fallacy if we argued that the Times was inspired by the candidates. This is not true. Left-lurching pundits and the Democratic candidates belong to the same herd and a common herd instinct guides them all. They need no orchestration and inspiration from each other. Other members of the herd, including people writing letters to the editor in your local newspaper, will pick up the call. The Times “analysis” is built around that single word, “invasion.” The authors elaborate their attacks with the assertions that the man they hate has filled his public speeches and Twitter feeds with “sometimes false, fear-stroking language even as he welcomed to the White House a corps of hard-liners, demonizers and conspiracy theorists shunned by past presidents of both parties.”

This elaboration relies almost entirely on inferences and vague generalities. Some members of this alleged corps are named, but no information about their exact view is supplied. The hard core of the accusations is the word invasion. Trump used that word. The “suspect” used that same word. Case closed. Verdict, guilty. No one is claiming that America’s supreme Twitter-babbler has explicitly advocated violence. Why bother? That pitiless word is enough.

This single example is intended to serve as a general warning. This popular fallacy will proliferate, and proliferate some more, during this period of boiling hot political antagonisms. Although I naturally prefer to belabor examples emanating from the left, I have to admit that you will see some from my side.

John Frary of Farmington is a former candidate for U.S. Congress, a retired history professor, an emeritus Board Member of Maine Taxpayers United, a Maine Citizen’s Coalition Board member, and publisher of FraryHomeCompanion.com. He can be reached at jfrary8070@aol.com