We have entered a disturbing new era. The sheer volume of false utterances and outright lies spewed during the United States’ presidential election campaign implies a growing disdain for factual knowledge, as does the proliferation of fake news disseminated without journalistic filters on social-media platforms such as Facebook and Twitter. By the time of the United Kingdom’s Brexit referendum in June, experts had already been deemed dispensable. With elites everywhere being accused of neglecting “real” people, frustration and anger are now trumping fact-based deliberation. In a climate of anxiety, confusion, and nostalgia for a fantastical past, raw emotion prevails. The rules of public discourse become obsolete, and the open horizon of possible futures is narrowed to a single escape route that fear-mongers portray as the only way forward. This is a poor way to cope with uncertainty, and it stands in striking contrast to the methods of science and free inquiry. In science, uncertainty is a powerful incentive for acquiring knowledge; indeed, it is the primary motivation for research, which is inherently uncertain. New discoveries often occur during open-ended explorations of the unknown. Scientists conducting fundamental research cannot predict what they will find or when they will find it. Many important discoveries are a result of serendipity: researchers find something unexpected that they were not looking for, but which they quickly recognize as significant. The scientific community rigorously seeks consensus about knowledge produced so far, but it knows that there is still much more to be discovered. All scientific knowledge is therefore preliminary, and will be extended, complemented, or replaced by new knowledge. At the same time, science and technology have enabled us to anticipate risks and identify additional unknowns. So, the more we know, the more we comprehend what we do not know. But, whereas the scientific community embraces uncertainty, remains ever curious, and is confident about the power of science and technology to create new opportunities for mankind’s collective future, other segments of society do not necessarily share this outlook. And it behooves scientists to understand why. There can be a fine line between experts’ prerogative to make technical judgments and non-experts’ prerogative to assess the consequences of those judgments. But between these positions lies a vast range of unintended consequences. When people translate knowledge into action, they initiate new interactions within complex systems, without necessarily knowing what the final consequences of those actions will be. Humans have evolved to understand simple cause-and-effect relationships. What we need now are more refined mathematical tools and simulation models to understand the hidden uncertainties that can emerge from interactions in complex social and natural systems. Likewise, humans have evolved to crave certainty. Past civilisations adopted certain practices in an effort to know the future. But, since then, humanity has made impressive strides away from believing in such destinities, and toward actively shaping the human condition. Science and technology were crucial to this progress, but they were not sufficient. We also needed new ideas about the scope of human agency. Encouraged by the achievements of modern science, we came to perceive the future as being radically open. Even though path dependencies, incomplete information, and cognitive biases can still frustrate human actions, we need no longer assume that past experiences must determine future outcomes. The future is inherently uncertain, which means that the present always could have turned out different than it has. Uncertainty is a cunning force in nature and lived experience. Its logic is always at work as we encounter constantly changing circumstances. It evolves and manifests itself in different ways: sometimes it challenges our assumptions and subverts our expectations; often, it takes us by surprise. Because of uncertainty, our achievements are not always what we intended them to be, and our lives are never simply routine. Uncertainty reveals opportunities to us that otherwise would have been wasted. Our lives are probabilistic, not determined, and the more we realise this, the less we need to feel threatened by uncertainty. Still, there is widespread disaffection today, and clever politicians are eager to exploit citizens’ anger. If people feel engulfed by crises, and view the future as fragile and precarious, they will be reluctant to embrace uncertainty. But this is where science has something to offer. Science makes visible that which would otherwise remain hidden. It alerts us to randomness in the physical and social world, and to the role that uncertainty plays in our communities and personal lives. By revealing the messiness of the world that we have created – intentionally and unintentionally – it allows us to imagine how we can create that world anew, even as we accept that the future will remain open and uncertain. - Project Syndicate