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Over this year there are a number of big general elections around the world that are set to pit extreme right against left in a way that will challenge democracy. The issues in the frame are populist's reactions against immigration, imposed responses to public health problems, involvement in other peoples' wars and managing climate change. These issues are particularly polarized in the U.S. election, in which the legitimacy of abortion is also up for debate. Science has a big part to play in defending democracy in these elections, but as a defender of facts, not values and preferences.

What allows science to deliver knowledge that works for policy interventions is not just that it is based on evidence carefully collected under controlled conditions but that it has to be corroborated in public. The requirements for repeatability and open assessment are the features in the invention of science that set it apart from knowledge made up for political and, for that matter, spiritual reasons.

There is a distinction, though, between getting the facts right and deciding how to respond to them.

Rarely will the science be unequivocal in terms of a policy outcome. This is because there is complexity in the cause-effect relationship behind the policy problems — variability in the responses of people and systems affected, and scientific uncertainties across both causes and effects.

Thus in the areas of those key policy issues that are prominent in the general elections, science can define the relationship between, for instance: the risks of abortion for mothers, but not their rights; the likelihood of survival of deep-frozen embryos, not if they are people; the consequence of vaccination, masking and isolation for public health, not whether they are acceptable, and the relationships between increasing greenhouse gases in the atmosphere and temperatures on Earth, and between increasing temperature and biodiversity and human health, not whether particular policies of mitigation or adaptation are right. More tenuously, with more uncertainty, science can define the relationship between immigration and the economy, and particular strategies of war and likely casualties, but in both cases, not whether the proposed policy solutions are acceptable.

This is not to say that science is unconnected with values. The most obvious one is that knowledge/understanding that is repeatable and works is deemed better than knowledge that does not. And in the same spirit: Fraud is bad. But these arise from the practical experience of science and why it has been successful as a human endeavor. They do not flow, as first principles, from any of the sciences.

So choices have to be made between the options that arise from the science. Preferences involve values. The presumption here is that in a democracy those will seek to reflect the values of the electorate.

The choices within the complex causal relationships behind the policy problems might be right- or left-leaning, legitimized by an electoral mandate, such as being spelled out by an electoral manifesto. For example, there would be an expectation that right-wingers would favor markets over governments in delivering decisions on public health and climate change, with left-wingers taking the opposite approach. This would be a legitimate exercise of political bias. However, to disguise value-laden decisions as being the outcome of science or as the outcomes of scientists representing a scientific point is a misuse of science and stands the chance of politicizing it. Technocracy of this kind has been a source of discontent and populism in the E.U. and U.S.

So what science provides is facts that can be use as basis for civilized discussion and debate as part of the electoral activities. It is the only good source of knowledge that works. It is an antidote to the involvement of misinformation in the political process. There needs to be better understanding of this through better science education at all levels. This is the way to defend a healthy democracy.

Peter Calow is a professor in the University of Minnesota's Humphrey School of Public Affairs.