The pandemic has put “evidence-based decision-making” in the spotlight. Every day, we see medical experts standing at the dais, shoulder to shoulder with government leaders who openly defer to them and claim to be following their advice.Ontario Premier Doug Ford's view is typical: “I will always listen to our health care professionals,” he says, “they are the experts when it comes to health care…”In fact, the reviews have been decidedly mixed. If political leaders want to bring public debate and decision-making more in line with scientific knowledge, they have some hard work to do. Here are three lessons that leaders and citizens alike can learn from the pandemic.Evidence Should Clarify the Truth Not Obscure ItLet's start with anecdotal evidence. One instance of a thing is not evidence of a trend, yet humans make this leap easily and often and politicians are skilled at exploiting it.Take Doug Ford's recent claim that weak border controls are a major cause of Ontario's high infection rates. As evidence, Ford points to a dozen or so passengers who arrived on flights from India with the B1.617 virus.If his argument has legs, it is not because of the evidence. A few infected passengers don't make the borders a sieve. Rather, the threat of infected travelers flooding across the border terrifies Canadians. In effect, the argument trades on fear, not evidence.Ford launched this attack after a disastrous week in Ontario politics. Critics say that his real goal was to divert attention from his troubles. In this view, he chose the border issue because it had the emotional amperage to jolt public attention away from Queen's Park and onto Ottawa.When the Trudeau government protested, Ford doubled down, speculating about the possibility of a “disastrous fourth wave.” In effect, he was using fear to create confusion and uncertainty – muddying the waters – so that Ontarians couldn't tell the evidence from the assertions.Our first lesson is that the human brain is hard wired to respond to unreliable patterns of evidence, such as anecdotal evidence. Because politicians are skilled at exploiting this, citizens must learn to recognize these tricks and resist them.While Science Separates Facts and Values, Politics Aligns ThemExperts say that politics should be led by science. While this is true, it can be misleading. Politics is not a science, nor should we try to make it one.Science organizes experience into two basic categories: subjective knowledge, such as values and emotions, and objective knowledge, including facts and evidence. It then uses facts and evidence to draw conclusions.In politics, drawing conclusions involves more than facts. It also involves taking a position on how people think these facts should align with their values.We see this in the pandemic debate over balancing the protection of public health with concerns about the economy. There are important tradeoffs between the two. Closing businesses harms people's livelihoods, while refusing to do so could lead to a spike in hospital admissions and deaths.Political leaders must weigh these risks, then decide which ones are acceptable. Facts about, say, community transmission can help inform their decisions, but facts alone aren't enough. Striking a balance also requires a value-judgement about which risks are worth taking.As a result, what looks like an unacceptable risk to a medical expert may look acceptable to a political leader who is weighing it against a community's livelihood.But let's be clear: we are NOT saying that politicians get to do whatever suits their values. We now know that some leaders relaxed mobility restrictions too early and that their communities suffered as a result.The lesson is that both facts and values have a role to play in weighing risks – and that political leaders still have much to learn about how to align values with evidence.Without Evidence Politics Reverts to TribalismA recent study shows that in many countries, including Canada, citizens are increasingly dissatisfied with their government's response to the pandemic. Many experts argue that it's because politicians have ignored the evidence.While we agree, let's note that experts can and often do disagree on what the evidence says, such as whether AstraZeneca is safe, whether schools should be closed, or if it is okay to go golfing.As people see this, there is a risk that their high expectations around science turn to cynicism – a belief that experts are as fallible or as fraudulent as the politicians they are supposed to guide. Rather than encouraging people to look to evidence to help find the truth, this could undermine the belief in a reliable standard for truth.There is some evidence that this is happening. Indeed, the Republican Party may be the canary in the coalmine. Donald Trump's Big Lie – that the 2020 election was rigged by Democrats – sets a new standard for truth that treats experts and mainstream media as frauds and encourages people to put their trust in leaders who believe in the Big Lie. This turns evidence-based decision-making into a form of group-think that now threatens American Democracy.Evidence is a critical part of the vaccine against tribalism. But it must be based on the right approach. The pandemic has shown how scientific knowledge is evolving – often daily – and that it is often incomplete.Rather than providing a solution, often it only points in a direction. This presents challenges to anyone looking for certainty, but it does not refute science or evidence. A reliable direction can be a huge step toward the truth.Our third and final lesson thus is that a commitment to the use of evidence in public decision-making should be tempered with a realistic understanding of the limitations around expert knowledge, the role that values continue to play in policy debate, and the complexity of many issues.Evidence can and should inform our public debates and decisions, but it is a mistake to expect it to solve them.Dr. Don Lenihan is Senior Associate at the Institute on Governance and an internationally recognized expert on public engagement, governance, and policy development. For more, visit his website at: www.middlegroundengagement.comAndrew Balfour is Managing Partner at Rubicon Strategy in Ottawa.