In this era of highly polarized politics, we appear finally to have arrived at an issue upon which both the Left and Right agree, namely, that “fake news” is undermining democratic discourse.

How can we prevent voters from being deceived by fake news? To this bipartisan concern, I offer a nonpartisan answer—education. Specifically, the country’s high schools and colleges should require a one-semester course in logic, with the high school course introducing students to the foundations of logic, and the college course deepening students’ understanding and critical-thinking capacities.

How would this help? The answer emerges when we review what logic courses teach with regard to “fallacies in informal language.” Take, for example, the logical fallacy known as the “argument against the person,” or, argumentum ad hominem. This fallacy takes the form of attacking the person making the argument, rather than the argument itself.

As Patrick Hurley’s Logic textbook notes, the argument against the person takes three forms. The first form, the “ad hominem abusive,” takes the form of verbally abusing a person who makes a contrary argument. For example, were the genocidal tyrant, Joseph Stalin, to argue that “2 + 2 = 4,” the fact that he was a mass-murderer does not undermine the truth of his claim, which is independent of his doubtless despicable character. Saying, “How can we believe anything this monster says?” does not address the merits of his mathematical claim. It may be psychologically powerful, but it is logically fallacious.

The second form of the fallacious argument against the person, “the ad hominem circumstantial,” does not abuse the individual in the manner of the ad hominem abusive; instead, it attempts to delegitimize an opponent’s argument through calling attention to the opponent’s circumstances. These circumstances are held up to argue that the opponent had to take the position he or she did; therefore, the opponent’s argument is held not to be credible. For example, someone can seek to discredit a political position through saying, “Of course you have to say that—you’re a member of the fill-in-the-blank party.”

A famous example of the ad hominem circumstantial is provided in Irving Copi’s Logic textbook: The famous abolitionist, Wendell Phillips, found himself on a train seated next to a group of Southern, pro-slavery ministers. The ministers baited Phillips in this manner: They asked him whether he gave speeches against slavery. He answered that he did. They then suggested that he go down to the slave South and try to make such speeches.

Comically, Phillips then employed the same powerful though illogical argument when he then asked the ministers whether they preach in order to save souls from Hell. They answered that they did. He then asked, “Then why don’t you go there?”

The ad hominem circumstantial can be a double-edged sword—and fun!

The third form of the ad hominem circumstantial, the tu quoque or “You too!” fallacy, attempts to portray an opponent as arguing disingenuously. Take the case of an alcoholic father attempting to teach his son the moral and health hazards of alcoholism. To the father’s admonitions, the son responds, “How can you argue against booze when you yourself are a boozehound?!” Of course, the father’s condition is irrelevant to the fact-based case he makes for the dangers of alcoholism.

These examples also show why illogical arguments can be so effective. We rightly look to the character of an individual when attempting to judge whether that person genuinely believes in what he or she has argued. This is natural and just. But the personal attributes of the speaker are logically irrelevant to the truth or falsehood of the propositions he or she expresses.

Another logical fallacy, that of “Accent,” manipulates word emphasis to imply a meaning that is quite different from the actual substance of an opponent’s claim. Copi provides another humorous example of this fallacy: A ship’s captain was enraged over the constant drunkenness of the First Mate. Therefore, each day the captain would enter into his official log the sentence, “The First Mate was drunk today.” Some time later, the captain fell ill and his duties fell to the intemperate First Mate. As part of his duties that day, the First Mate was required to enter the day’s events in the captain’s log. The First Mate wrote in the log, “The Captain was sober today.”

The First Mate’s choice of emphasis, or “accent,” suggests (comically) that the Captain was nearly always intoxicated.

Finally, we turn to the logical fallacy that is perhaps most pertinent to citizens of a self-governing republic—the argumentum ad populum, or “appeal to the people” (also known as the “bandwagon effect”). This is especially relevant for us in light of the power exercised in our culture today by opinion polls. The 19th-century political philosopher, Alexis de Tocqueville, argued that America, which had dispensed with both monarchic and ecclesiastical authority, was left with no one but equal citizens. This is all to the good, he argued. But he also foresaw the problem it raised: In a country of equal citizens, he predicted, majority opinion would come to exercise a near-omnipotent effect on individuals. As the late Alan Bloom quipped, “Look to Gallup, before you leap.”

No one ever wants to be on the wrong side of popular opinion. How many times have you heard arguments “won” through this statement: “Well, Senator, 58% of American’s do not agree with you about fill-in-the-blank issue”? The assumption behind this response is that whatever policy a majority agrees with, is justice. Of course, this judgment does not follow from what may well be a true statement about polling results. Such arguments move us because we assume Vox populi, vox Dei—“the voice of the people is the voice of God.” This is why the fallacious appeal to the people is so powerful.

This fallacy was in fact the position taken by Stephen Douglas, who lost to Abraham Lincoln in the presidential election of 1860. Douglas’s proposed remedy to the slavery dilemma was “popular sovereignty,” by which he meant that each new territory that was being admitted to statehood in the United States should decide for itself whether to be a free or a slave state. For Douglas, the fact that in each new state the slave-or-free decision would be decided by the majority made it de facto just—because it was democratic!

Thankfully, Lincoln was able to show that Douglas’s argument for the unqualified justice of a majority decision—any majority decision—was morally indistinguishable from the tyrannical maxim, “Might makes Right.” After all, in a democracy, the majority has the might, which in Douglas’s rendering made any majority decision—be it to honor the Declaration of Independence’s promise of equality or to honor the slaveholder’s devotion to mastery—equally “just.”

Lincoln showed that democracy must be governed by a transcendent standard—one recognized as superior to any and all majority decisions—if democracy is not to degenerate into what Lincoln called “mob-ocratic rule.”

In short, logic teaches us that even if the whole world thinks 2+2=5, that doesn’t make it so.

All this leads to my modest proposal: To combat the pernicious effects of “fake news,” let’s educate young people to spot a phony argument when they see one. Let’s arm today’s students, who will be tomorrow’s leaders, with a foundation in logic.