What does evidence-based policymaking have to do with the politics of hope and fear? More than you might think. The recent campaign battle between Justin Trudeau and Stephen Harper offers a glimpse into a major shift in policymaking now underway in governments around the world.Throughout history, reliable evidence has been in short supply on most issues. Policymakers tended to fill the gaps with makeshift principles, anecdotal evidence, speculation, religious doctrine or ideology. As a result, history is filled with bad policy.That could be about to change. For the first time, governments have—or soon will have—a super-abundance of data and information that could usher in an era of enlightened governance.Consider the Green Revolution of the 1950s. By letting science guide policy, governments tripled global food output in a decade. The challenge now is to extend this revolution to economics and social policy—and that shifts attention off hard science and onto the soft ground of human behaviour.Humans are “intentional” creatures, which is to say that we form ideas and plans that we can then choose to act on. The social and psychological conditions involved can be devilishly complex.Nevertheless, through the magic of Big Data governments' ability to use policy to shape public behaviour is growing by leaps and bounds. And that is where fear and hope come in.Fear is a primordial emotion that easily overwhelms our capacity for intentional action and, in its place, triggers instinctive responses. Thus, when people are scared, they tend to run first and think later.Hope is a different kind of experience. It is “aspirational” in the sense that it combines emotion with intentional action. It not only calls on us to imagine a situation that is better than the present one, but to recognize that we are instrumental in realizing it. It empowers us by challenging us to make a plan and seize control of our future.There is a longstanding debate over which of these two sides of our nature—fear or hope—should guide policymakers. We can call the first one the “behavioural psychology approach.”Behavioural psychology tends to see humans as creatures of reflex and routine. We may be intentional, but we usually act out of habit, custom and settled beliefs, much of which has been codified in simple behaviour-patterns and anchored in instinct and emotion.This was the model behind Stephen Harper's politics of fear. He aimed to move voters into the Conservative camp by focusing on hot button issues like terrorism or financial chaos and crafting a message around them that played to our fears.Of course, this is hardly new. Political strategists have used public opinion research to find hot button issues for decades. But Big Data is moving this to a whole new level.Researchers are using datasets to identify and map all kinds of behaviour-patterns (and their triggers), much as biologists mapped the human genome. As these come available, they provide the basis for a new approach to policy, perhaps best known as Nudge Theory.The idea behind Nudge is to design policy around key behaviour-patterns, then “package" the message in a way that triggers these behaviours. This, in turn, allows governments to align public behaviour with their policy goals.For example, how vegetables are arranged on a supermarket display counter affects customers' choice. By researching how people react to different arrangements, policymakers were able to single out the ones that got people to make more healthy choices.The UK, a leader in this field, is already applying the Nudge model to national policy in a wide range of areas, including Health, Energy, Education, Security and Taxation.Finally, Big Data comes with an impressive new delivery system for “micro-targeting.” In recent campaigns, political parties have begun using social media to target increasingly smaller audiences with increasingly fine-grained behaviour-patterns and personalized messages. This is proving to be a highly effective way of shaping behaviour—and of winning elections.Nevertheless, lots of policymakers are looking beyond behavioural psychology. Their alternative, which we can call the “progressive approach,” aims at using Big Data to increase our collective capacity for planning and decision-making, that is, for intentional action.Progressives have always believed in social progress and in government's role in promoting it. Historically, education has been their preferred option because it builds the capacity for reflection, which, in turn, advances intentional action.Now progressives are waking up to a new idea: Big Data could be the tool of the future. Like behavioural psychologists, they want to use it to change policy, but not just through instinct and emotion. They believe it can also be used to engage the public more fully in the policy process, which, in turn, will produce a quantum leap in our collective capacity for planning and decision-making.Dialogue and evidence are the keys to this. New kinds of dialogue processes are being designed and tested that engage people in a methodical way and allow them to work through issues on their own terms and together with others like themselves. Big Data provides the evidence they need to guide the discussion, rally the participants around the best decisions and, ultimately, to get real results.Trudeau's campaign was a big help in getting the progressive approach into the spotlight. Before the campaign, he spent two years traveling the country and engaging Canadians on the ideas that would eventually make their way into the Liberal's campaign platform.During the campaign, he talked about hope, but he was also clear that this is only the first step in good governance. Hope must be followed by planning and action. And that takes political leadership, open dialogue and evidence-based decision-making.This message not only contrasted sharply with Harper's politics of fear—and with the behavioural psychology behind it—it resonated with Canadians. The challenge for Liberals now is to govern the way they campaigned.Finally, let's be clear that these two models are not exclusive. Nor is one right and the other wrong. All governments should be pursuing both. The real debate is over the degree to which governments should favour one over the other and where.For many governments, the Nudge model is highly appealing. They are more comfortable marketing policies to the public than engaging them in the policy process. That requires a high level of confidence in citizens and a deep trust in democracy, something that is often in short supply among leaders, as we saw with the Harper government.Nonetheless, history is on the move. Governments everywhere are coming to a fork in the road and they will have to choose. Which way will Canada go?Dr. Don Lenihan is Senior Associate, Policy and Engagement, at Canada 2020, Canada's leading, independent progressive think-tank. Don is an internationally recognized expert on democracy and Open Government. He is currently the Government of Ontario's principal advisor on its Open Dialogue Initiative. The views expressed here are those of the columnist alone. Don can be reached at:[email protected] or follow him on Twitter at: @DonLenihan