Among Donald Trump’s accomplishments is inadvertently stimulating popular interest in epistemology. “Post-truth” is the Oxford English Dictionary’s 2016 “word of the year”—a judgment based largely on the number of times it’s been invoked by journalists discussing the politics of the UK European referendum and the US presidential election. In a post-truth world, politics is conducted in a frenzy of self-reinforcing bubbles; people’s psychological preference for information that reinforces their pre-existing biases means that the media gives us the stories we’ll like rather than the ones that are necessarily true.

2016 was also the year in which “fake news” entered the political lexicon. Initially used to describe the literal manufacturing of lies masquerading as factual reporting by Macedonian teenagers trying to make a quick buck or Russian agents out to cause trouble, President Trump has now seized on the term to attack any media story, or even polling data, that he doesn’t like. Even cynical Washington insiders have been taken aback by the Trump administration’s apparent indifference to truth. Trump’s bizarre insistence that his inauguration crowd was larger than Barack Obama’s in spite of the photographic evidence to the contrary is reminiscent of Marx’s famous injunction in his core text “Duck Soup”: “well who you gonna believe, me or your own eyes?”

This is a slightly different variant of dystopia from that famously described in George Orwell’s 1984, which leapt up the best-seller lists on Amazon after the President’s advisor Kellyanne Conway defended her boss by saying he had “alternative facts”. Orwell’s imaginary government wanted people to believe that war was peace and freedom was slavery, whereas today the problem is that no one knows what to believe any more. It is as if the proliferation of data on the internet combined with distrust of institutions and “experts” has led to epistemological anarchy: a state in which it’s simply too exhausting to keep on fact-checking everything so you just shrug your shoulders. You keep on hearing people arguing about it, so who knows if there is really man-made climate change or not?

Sir Richard Evans, formerly the Regius Professor of Modern History at Cambridge has claimed that the origins of the “post-truth” culture lie in the pernicious influence of postmodernists who dismissed the pursuit of truth as a delusion.

Of course there is nothing postmodern about the phenomenon of the powerful trying to control knowledge: that desire is surely as old as government itself. “We live in an age that maketh truth pass for treason,” said Algernon Sydney on the steps of the scaffold in 1683—a line that helped his version of truth posthumously triumph, not least in eighteenth- and nineteenth-century America where he was hailed as a Whig patriot who’d been martyred for the rights of the people. Sydney’s valedictory bon mot might have struck a chord with the acting Attorney General fired by President Trump for her “betrayal” when she told Justice Department lawyers not to contest his ban on migrants from seven majority-Muslim countries.

So the epistemological problem of how we know what we know has bedeviled philosophers for centuries. It was all very well for Enlightenment thinkers to tell us that our reason should lead us to truth, but what if one person’s reason leads them to a truth that another thinks is a lie? What if, as Kant suggested, we never actually “know” a thing in itself but only as filtered through our categories of understanding?

There is probably some truth—a deliciously ironic truth—to the idea that the cultural ascendency of postmodernism, which was intended to emancipate us from oppressive narratives about the world, has provided, knowingly or otherwise, some of the modes of argument for the populist Right. Conservative talk-show hosts in the US sought to emancipate their listeners from what they saw as hegemonic liberal narratives through a radical skepticism about authority. It is a short step from here to the view that one “knows” something is right because one “feels” it to be true—that appeals to evidence that is not in front of your own eyes (as “experts” are wont to do) is itself a part of the liberal domination that has to be overcome. Trump’s politics has its origins in that kind of thinking.

Good historical writing can be an antidote to “post-truth” culture, not because historians have magically resolved the epistemological challenges of generations. But because they have a pragmatic, practical answer: while on the one hand historians are professionally dedicated to never taking received narratives at face value; on the other, they are equally determined to use an exhaustive search for evidence to construct the most plausible meaning they can. Reading and doing history is empowering because it does not just give you the tools to doubt what you’re told, but the tools to build something back up instead.

Historians cannot fight the battle for truth alone, of course. Without a free press and serious journalists dedicated to holding power to account, and without institutions like universities that try to maintain the spirit of scientific enquiry, the space for historical analysis withers. But history does teach us that while omniscient objectivity may be a noble dream, the rigorous and transparent use of evidence is something we can choose to do, or not.

This is a version of a  piece I wrote for BBC World Histories magazine for their February 2017 issue.