Each week, In Theory takes on a big idea in the news and explores it from a range of perspectives. This week we’re talking about voter rationality. Need a primer? Catch up here.

David Greenberg is a professor of history at Rutgers University and the author, most recently, of “Republic of Spin: An Inside History of the American Presidency.”

For years after Americans elected Ronald Reagan president, liberals were despondent, doubting the electorate’s capacity to make sound judgments. Here, in their view, was a not-very-bright former movie star who showed no grasp of policy, only a reflexive right-wing ideology. Surely, many argued, people were deluded by his skills as a communicator, getting them to buy into delusions like supply-side economics and the Star Wars missile defense system.

Several years later, when Bill Clinton — enjoying greater popularity as president than Reagan had — withstood an all-out impeachment attempt, it was conservatives who questioned the good sense of the American public. Here, they said, was a small-time huckster and philanderer who lied under oath and showed no respect for the rule of law, but was getting away with it either because of his political dexterity or the vibrancy of the economy.

It seems possible that our periodic crises of faith in the wisdom of the masses are rooted not in any cold-eyed account of human nature, but rather in our fluctuating judgments of whether or not we agree politically with the choices they make.

While researching for my recent book, “Republic of Spin: An Inside History of the American Presidency,” I found a continuing anxiety through the years that spin — whether it was called propaganda, publicity, news management or something else — would subvert the public’s ability to make rational, independent judgments. There’s a fear that in the face of the ever-more sophisticated techniques devised by professional spin doctors, voters are becoming increasingly malleable. They fall prey to manipulation of their emotions, dishonest rhetorical appeals or faulty claims about issues they are in no position to sort out for themselves.

Our anxiety about illegitimate persuasion returns time and again — it’s as regular a feature of American politics as convention balloon drops, Fourth of July parties and sex scandals. In the 1920s, Walter Lippmann rejected the idea of an “omnicompetent” citizen who can stay well-informed enough to form opinions on the increasing welter of policy issues confronting the nation. This led him to temper his belief in democracy with a strong guiding role for disinterested policy experts.

In the 1950s, Vance Packard fretted about the insidious psychological techniques that advertising wizards were using to play upon our unconscious. In our own time, Stephen Colbert coined the term “truthiness,” to direct our attention to people’s willingness to believe what feels true over what really is true.

A host of overlapping fears underpin these critiques: Will people be swayed by emotion and political bias, rather than cold reason? Does the public have adequate defenses against politician who spin, lie, or otherwise play with the truth? Does the complexity of modern life place the analysis of policy beyond the grasp of all but the most dedicated full-time student of public affairs?

It would be naïve to dismiss these concerns. The past provides many examples of the public following its half-baked enthusiasms and its overwrought fears, its blind partisanship or its ill-founded moralism. People have been deceived by politicians who’ve shaded the truth.

Yet it would be wrong to aspire to a political world devoid of appeals to emotion, stripped of rhetorical claims that slant the facts, or reduced to expert pronouncements issued from on high as to which policies make sense and which don’t.

For one thing, the lines are hard to draw: Where does emotion stop and reason begin? Where does fact end and interpretation start? How much detail do we need to know to consider ourselves informed?

Democratic politics depends precisely on not limiting public judgments to only the most bloodless, rational calculations. We rely on politicians’ rhetoric to inspire us — and even to scare us about things we should genuinely fear, like the curtailment of long-held rights or the evisceration of valued social programs. We similarly need to grant politicians a margin of exaggeration and even dissimulation in our political discourse, because they must be free to advocate full-throatedly for their passions and draw sharp distinctions from their rivals. And we want voters to form judgments on imperfect knowledge, lest the demand for consummate mastery of the issues chill our democracy into a technocracy.

Journalists and intellectuals should — and do — call out politicians when they distort, exaggerate, or manipulate our hopes and fears. In an aphorism usually attributed to Daniel Patrick Moynihan (but first coined in slightly different form by Bernard Baruch), “everyone is entitled to his own opinion, but not to his own facts.”

The problem is that determining which facts are relevant or important to a political debate is part of the challenge — and often the heart of the disagreement. Instead of trying to somehow banish emotion and spin and other less rational elements from the kingdom of politics, we’d be better off trying to inculcate in our fellow citizens a critical sense that helps us question and evaluate politicians’ claims — and maybe, just once in awhile, to know when to believe in what they say.

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