“Who does not understand should either learn, or be silent.” So said John Dee, the Elizabethan mathematician and astrologist. Dee’s interest in occultism, his evasive public character, and his association with Rosicrucianism (a 17th-century predecessor of Freemasonry) made him a key figure in early conspiracy theorising. He died in 1608. Since then, conspiracy theories from the Illuminati to the global warming hoax have challenged conventional facts and histories in Western democracies. Can such theories purport to understand the world? Are they dangerous for democracy? Is it always bad to mistrust politicians and the media?

Social media and political spectacle have allowed conspiracy theories to flourish: googling ‘US election conspiracy theories’ produces stories that Clinton is a satanist, Trump is a plant working for Clinton, Clinton is dead. Crafted from disconnected events and visual symbols, conspiracy theories reveal a deep mistrust of political elites, claiming to know what’s really going on.

Yet while some are far-fetched and ridiculous, others are more moderate, based on kernels of truth – such as the theory that the media played a part in determining the outcome of the election. In a talk given at the London School of Economics in February, David Runciman, professor of political theory here at Cambridge, questioned whether being suspicious of the status quo was always a bad thing: in investigative journalism, having a ‘hunch’ is a prerequisite to uncovering new information. Had journalist David Conn and others not held the belief that the police and The Sun newspaper were staging an orchestrated cover up, would the truth about Hillsborough have come to light? In cases such as these, holding a suspicion of received facts can prove prescient.

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Cambridge-based project Conspiracy and Democracy has found that working-class men are those most likely to believe in conspiracy theories. This is unsurprising: those who feel like there is an injustice being committed towards them are more prone to buy into narratives explaining that injustice. But this tendency also describes the nature of the systems under scrutiny. The complexity and bureaucracy of political processes and big businesses make these institutions impenetrable to outsider understanding, and does not offer individuals to blame. Casting around for culprits, it is unsurprising that many choose appealing, comprehensible fables to explain the macro forces at play.

Conspiracy theories presuppose an understanding of complex systems and interactions that a person cannot purport to know. They populate a landscape of competing positions where truth has no bearing on legitimacy, weaving a tapestry of polemical narratives. Occasionally, these narratives might map onto reality – but their veracity will always be judged on how compelling they are as stories, not whether they tell us something real about the world.

When we throw truth out with the bathwater, informed decision-making goes with it. Democracy relies on having the facts that a sea of competing untruths cannot provide.

By rejecting political conversation mediated by facts, conspiracy theorists abstract themselves from reasoned public debate. This ‘outsider syndrome’ goes part of the way in explaining Trump’s rise to prominence. Trump is able to say things regardless of their truth value, and garner popular support for doing so, because he rejects the political system that criticises him. As a populist with no regard for truth, he performs the role of a political outsider who exposes the inner workings of a corrupt elite.

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Trump himself is aware of this potential. He voiced suspicion – ironic, in hindsight – that the whole election was rigged. In a rally this September in Kenansville, North Carolina, Trump told supporters: “We know it’s a rigged system. All you have to do is ask Bernie Sanders and you’ll see.” Presumably he is less concerned about the ‘system’, now that he has won. But insidious remarks such as this undermine people’s belief in the legitimacy of the election process. They fuel unjustified suspicion that the system is broken and corrupt, colouring democratic decisions.

Conspiracy theorists reject the possibility of positive change until an entire system has been exposed and overturned. Tying the possibility of progress to a distant hope, as they do, makes positive change a thing beyond one’s own control.

Demanding change is vital to a healthy democracy, as it holds powers to account and shows that alternatives exist. Rejecting the possibility of improvement until total institutional change has been achieved will discourage people from campaigning for vital political improvements