When medical students in the Middle Ages opened a body and pointed out discrepancies between what they saw in front of them and the traditional descriptions of Hippocrates and Galenus, they were reprimanded by their teachers: “Would you trust more your fallible eyes than the wisdom of the ancients?” It was only in the 16th century that Andreas Vesalius, father of modern anatomy, established the revolutionary medical notion that observed facts should outweigh received beliefs. Thank Vesalaius the next time your doctor prescribes you a pill or an exercise regimen rather than a leech or a purge.

The parts of the world we call “modern” are based on the seemingly simple, but once radical, idea that there are things called facts—assertions that are not only objectively true, but also can be verified. It’s easy to miss this, easy to believe that modernity is mostly like ancient times except for penicillin, cars, and Wi-Fi. In truth, the technological progress only came because the core assumptions changed first.

The scientific explosion that began in the Enlightenment and accelerated during the Industrial Revolution was part of a larger cultural shift in how Western cultures thought about truth and authority. The changes began during the Black Death in the 14th century, a horrifying trauma that upended whatever sense Europeans might have had that their traditions explained the world around them. This new questioning of received wisdom, born in tragedy, blossomed into the Renaissance, the Reformation, and the Age of Discovery. Western Europe developed an eagerness to question traditions, no matter how ancient, look for evidence, and listen to arguments from anyone, no matter their social status, as long as they had good evidence and a good argument. Such arguments did not always remain peaceful, and widespread disgust with the religious wars of the 17th century brought the secular state into being, paving the way to further changes that reshaped Western societies from top to bottom. The scientific method and all its fruits, democratic government, and the pursuit of systematic economics, whether capitalistic or socialistic, are all outgrowths of the one root of modernity: the claim that there is truth, and that truth is accessible to us through reasoning and experimentation. In modernity we may have opinions, but, no matter who we are, the authority of our opinions depends (at least in part) on whether they are compatible with true, observable facts.

* * *

In the 21st century, however, the modernity has yielded more and more to the postmodern, and facts are out of fashion. More in vogue is the concept of multiple “narratives”—the idea that there are no objective truths, but rather only subjective stories built to justify the narrator’s preferred actions and opinions. In this framework, no narrative can claim to be truer than others are.

This notion is inescapable in dialogue about the Arab-Israeli conflict. Often I find myself arguing with anti-Israel activists, and when I reference historical facts such as, say, the UN partition plan of 1947 or the Arab invasion of 1948, they invariably retort: “Well, that’s the Zionist narrative; the Palestinian narrative is different.” But the vote to partition British Palestine in 1947 is not a “narrative.” It is an historical fact.

That anti-Zionists should embrace the language of competing narratives is not surprising. The postmodern (really pre-modern) idea that narratives trump facts emerged in far-Left circles deeply influenced by post-colonialism. The political Right, however, has adopted this framework with the convert’s zeal. Neil Newhouse, a Romney strategist during the 2012 campaign, set the tone for future anti-factualism when he said, “We’re not going to let our campaign be dictated by fact-checkers.” (In other words, we will disregard the truth whenever it’s useful.) Four years later, we have seen an astonishing defeat for facts in the political arena, made manifest in the victory of Donald Trump, a candidate whose relationship with facts (it needs hardly to be said) is not even hostile, but more like absentee.

Democrats (and the legion of Trump’s failed Republican rivals) shouldn’t take this as their cue to feel superior. Most of us have a bit more of a tether to reality than The Donald, but we all share the tendency to avoid or ignore facts that don’t agree with our preconceptions. Thomas Kuhn called it “paradigmatic blindness”. Our beliefs and values act as a filter that screens out information that threatens our certitudes. Cognitive scientists call it “confirmation bias,” meaning that our brains will subconsciously select data that strengthen our existing convictions. This mechanism is, as best we can tell, universal to humankind, largely automatic, and sometimes necessary for processing the myriad of stimuli that our brains receive. We are not necessarily aware when we are ignoring evidence that contradict our beliefs.

The gift of modernity was not to erase these biases, but to acknowledge them and attempt to correct for them—to remind us that we should strive to pay attention to facts even when they are inconvenient to our beliefs. Biases are human nature, not a new invention of postmodernity. But what is new today, and much more dangerous than subconscious bias, are postmodern ideologies that openly accept, or even celebrate, disdain for the facts. Modernity, drawing on the riches of Renaissance Humanism and the Enlightenment, believed in the human capacity to think rationally; postmodernism, unwilling to listen to Popes or Bibles, but also thinking much more negatively of humanity as a species than the Humanists did, simply throws up its hands and gives up on both reason and tradition alike.

The result is a phenomenon called “epistemic closure.” It sounds like some gastrointestinal obstruction, but what it means is that some people create belief systems that are entirely closed systems of deduction unaffected by empirical observation and impermeable to facts. Taking a step beyond trying to be rational while being accidentally held back by bias, when we embrace epistemic closure we consciously know that the facts disprove some of our beliefs, and we willingly choose to ignore those facts anyway. Taking a step beyond confirmation bias on the subconscious level, we actively “unfriend” those who disagree with us on social media, and we actively make sure not to let our ears and eyes be polluted by the TV and radio channels operated by political opponents. When we can’t avoid it, and are forced to confront adverse facts, we dismiss them as part of a conspiracy theory (Obama’s birth certificate is forged! Monsanto or vaccines cause autism!), or we defend our position with the ultimate claim of immunity to objective truth: “I just know it.”

The reasons for cocooning ourselves in epistemic closure are diverse: a desire to reduce the scary complexity of the world down to simplicity, the self-reinforcing nature of the echo chambers that most of us have now constructed for ourselves, and the simple fear of admitting that we are wrong. In a series of studies in 2005 and 2006, researchers at the University of Michigan found that when misinformed people, particularly political partisans, were exposed to facts at odds with their opinions, they rarely changed their minds. To the contrary, they often became even more strongly set in their beliefs. Facts, the studies found, do not cure misinformation. Like a partial dose of antibiotic, facts can actually make the disease of misinformation even stronger. Political scientists know this phenomenon as “backfire,” but the ancients knew it as pride. The fear of admitting that we are wrong makes us entrench even more in our false notions. The more wrong we are, the more embarrassing it would be to admit making the mistake, and so it is regarding our most egregious mistakes that we are most unlikely  to change our minds when confronted with damning facts.

Whatever the mix of causes, now that we have become the willing co-conspirators of our own biases, the idea that invented modernity—that facts should inform our decisions —is rapidly losing ground. Needless to say, this dynamic doesn’t bode well for American democracy.

* * *

In the Jewish community, we suffer from this malady as well. As we become increasingly polarized, especially around Israel, more and more our opinions are formed within closed circles of people who think like us. We, also, are too proud to admit when facts prove us wrong. We, also, see the world changing around us and seek refuge in artificial simplifications of that reality.

During the Iran Deal debate, this phenomenon was brutally evident. Both sides argued their cases without even wanting to know, let alone understand, the very complex facts. Much easier to “go with your gut” than to try to understand how a nuclear centrifuge works. Whenever somebody would present a set of facts we didn’t like, we branded them “warmongers”, “traitors,” or holders of “dual loyalties”.

When it comes to the debate around BDS on campus, the willful ignorance of fact runs rampant. The BDS movement is itself, by and large, divorced from fact. Comparing Israel to South Africa, let alone Nazi Germany, has no factual basis and requires a willing ignorance of reality. But many of the anti-BDS efforts are also based more on ideology than fact. We have ample evidence, for example, that most students are liberal or progressive, yet we keep associating the pro-Israel message with the political right. We know that weakening the historical alliance between Jews and progressives is self-defeating in terms of BDS, yet, we take a fully ideological approach and let that alliance crumble.

Jewish students tell us, time and again, that silencing their debate and preventing them from engaging with Israel in a loving yet critical manner pushes them to apathy, or, worse, into the BDS camp. Yet we keep pounding them with “talking points.” We also know, from multiple studies on the development of Jewish identity, that using “fighting BDS” as the sole point of entrance into campus Jewish life is a losing proposition. Yet we keep defunding Jewish identity programs and lavishly funding anti-BDS initiatives that demand that students become our “foot soldiers.” Despite all evidence, we continue to believe that if we only use different “messaging” for the same old case we’ve been making, all our problems will disappear.

In the anti-BDS movement, sometimes the ignorance of facts reaches nearly comic dimensions, as in the case of a decision by JNF Canada to withdraw sponsorship of a concert that included the Israeli singer Noa, whom they considered a supporter of BDS—despite the obvious fact that Noa, like every Israeli artist, is herself a victim of BDS. (She has also strongly denounced BDS as hypocritical and counterproductive to peace.) Another infamous demonization campaign against the New Israel Fund, which also smeared some venerable communal leaders with a false anti-Israel label, was likewise based on accusations utterly remote from reality.

As in politics, the world of philanthropy seems particularly susceptible to developing an allergy to facts. Some funders seem to compartmentalize their brains: they prefer facts and evidence when it comes to business, but act completely irrationally when it comes to philanthropy. The structure of incentives and feedback mechanisms in philanthropy, as in politics, doesn’t help matters. If you ignore the facts in your business, you go bankrupt. But if you ignore the facts in philanthropy and make a bad grant, you get a gala in your honor. And if you ignore the facts in politics, you win a major party’s nomination for the presidency.

* * *

What can be done about the world’s betrayal of the core idea that built its greatest wonders? For now, I will speak only about the sphere in which I am most deeply engaged: the Jewish philanthropic and communal field.

Funders have a duty to strive to bring facts and reason back into their proper places. At the very least, it is our task to work for a rational, facts-based approach to Jewish philanthropy. Funders rightfully pick causes that match their passions, but they must be willing to look at facts about those causes dispassionately. Philanthropists should fund programs that are objectively effective, not only what makes them feel good. All of us in the philanthropic and Jewish communal world need to embrace facts that make us uncomfortable and threaten our certainties, because that’s the only way in which we will learn anything new. We need to work consciously and conscientiously to break through our confirmation bias and tear down the echo chambers that shield our minds from the world. We have no alternative if we really want to solve the many challenges that our communities face. A philanthropy that is guided by a healthy combination of facts and passion will be more effective than one guided by untested ideological assumptions. The much-beloved strategy of seeing the world as we want it to be, and not even bothering to ask how it really is, will be a waste of precious resources at best.

Bringing facts into the debate is counter-cultural today in America, because the ongoing political climate seems to show that ignoring the facts pays. But Jews have long experience in being counter-cultural. We have played that role in many key moments of history. It’s even inscribed in our very name as a people: we are the “Hebrews”, those who are on “the other side.” This is not a particularly comfortable calling. It takes courage to face our fears of being wrong, and to consider abandoning courses of action in which we are emotionally involved. It may be painful to contradict those who are ideologically close to us and, in a tense atmosphere, to risk ridicule and anger.

But the only alternative is the self-defeat of the postmodern option: ignore the facts, and face the consequences when they come. And come they will. As Albert Einstein said, reality may well be “merely an illusion,” but it’s “a very persistent one”. Or, as John Adams put it, “Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence.” We humans are pretty stubborn things ourselves, but, sooner or later, reality will catch up with us, and if it catches us napping, we may not like the results. Narratives and philosophical niceties notwithstanding, the only real question about facts is whether or not we’re willing to face them.