Most of the recent worries over the spread of propaganda have concentrated on the use of social media: WhatsApp, Facebook, Twitter and YouTube have all been rightly criticised for their use in spreading misinformation. Less attention, perhaps, has been given to the content of the messages and the strategy behind their use. The template for many modern campaigns of disinformation was invented by the tobacco industry as it fought against the mounting evidence that it was selling a product that killed its users.

The “tobacco strategy” as researchers christened it, relied less on outright lies than on confusion and irrelevant truths. For example, the tobacco industry funded first-class research into the harmful effects of asbestos to produce the impression that all kinds of things gave you cancer – so why worry about the ones that give pleasure as well?

Now this strategy has itself been scientifically examined, with disturbing results. Three philosophers of science, James Owen Weatherall, Cailin O’Connor and Justin Bruner, have modelled the ways in which scientific results can influence policymakers. They show that it is perfectly possible over time for almost all the policymakers to end up convinced of something that almost all the relevant experts believe is untrue. This is especially likely if there are propagandists operating for the wrong view and the science is difficult or disputed. This model fits the tobacco controversies very well, but it has obvious further applications – to climate change and perhaps to some political questions too.

The fact that the science is difficult and the results disputed does not mean there isn’t a right and a wrong answer. Just because experts disagree in good faith does not mean that they are all equally likely to be right. Tobacco is in fact a lethal drug. The world is in fact warming very dangerously as a result of human actions. But the process by which scientists reach consensus on these matters is slow, and prone to misinterpretation from the outside.

The paper shows that when neither the scientists nor the policymakers have access to all available research – which is true of all important questions – they rely on their social networks to sample the knowledge for them. This sample can be biased either at random or as the result of deliberate action. Propagandists for one side or another can present decision-makers with a flawed picture of the state of knowledge. This is much more effectively done – their models show – by omitting unhelpful results than by inventing helpful ones. The tobacco companies sponsored lots of research but only published the findings that helped their cause.

Unscrupulous journalists may make this worse by withholding from their readers stories that spoil the picture they want to present. But even some non-partisan reporters may run into another danger. Attempts to present “both sides” of a question when there is no real dispute among experts can be just as deceptive as outright propaganda. Either way, the public is misled and the wrong decisions are made.

This isn’t an easy problem. We need experts to make judgments about which problems are contested and which stories are significant, but what happens when these judgments are rejected? Reaching the truth demands a community of trust, and to build this is a project for everyone involved, not just for experts. Experts deserve to be believed because they are unlike the rest of us – they are in the relevant fields better at finding the truth. But in reality they will be believed only to the extent that they are seen to share our moral values and concerns.