SYNDICATE. The word alone evokes thoughts of skullduggery, self-interest and string-pulling in the shadows – usually those inky black ones you find in eerie underground car parks.

Put all that in a TV series about unexplained paranormal events and sinister government departments, give the word a definite article and a capital letter, throw in faceless agents with quirky character names such as X or Well-Manicured Man, and you have a plot device so big and sticky that any and all conspiracy theories will adhere.

Fans of Chris Carter’s 1990s phenomenon The X-Files know all about this. And they know all about The Syndicate, the half-glimpsed, multi-headed organisation whose nefarious activities gave the show its over-arching narrative during a nine-year, 208-episode run.

For a pre-Y2K world also assailed by apocalyptic films about angels (there were loads: don’t you remember?) and worried about “End Times” prophecies and the Millennium Bug, the world of alien conspiracies and government cover-ups portrayed in The X-Files was all too easy to swallow. It still is, which is one reason we’ll be tuning in tomorrow when a new series of The X-Files begins on Channel 5.

The long-awaited franchise reboot features almost all the favourite characters from past series. Walter Skinner and Smoking Man – FBI Assistant Director and creepy bad guy respectively – are back. So are nerdy conspiracy theorists The Lone Gunmen, even though they died at the end of season nine (and their spin-off series with them). And, of course, we hail the return of David Duchovny as FBI Special Agent Fox Mulder, who believes in the supernatural, the paranormal and the extra-terrestrial, and Gillian Anderson as arch-rationalist Dana Scully, his initially sceptical colleague and sometime love interest.

As with the previous series, the new six-parter alternates between what are known as “monster-of-the-week” and “mythology” episodes, a televisual technique Carter pioneered.

The first are single episodes in which Mulder and Scully tackle Something Unexplained (in previous series you could take your pick from: Satanists, shape-shifters, evil gargoyles, a half man-half flukeworm creature that lives in the sewers and comes up through its victims’ toilets and fan favourite Eugene Tooms, an orange-eyed ne’er-do-well who eats people’s livers and can squeeze through the narrowest of gaps).

The second type drop a few more pieces into the jigsaw that is the bigger picture, moving forward the show’s long-running story about The Syndicate’s attempts to cover up the existence of alien life following the 1947 Roswell Incident (the Year Zero moment for conspiracy theorists: a UFO crashes in New Mexico but the US Air Force claims it’s a weather balloon. Yeah, right).

In one sense, then, little has changed. But nearly a quarter of a century after The X-Files first whetted our appetite for conspiracy and cover-up, does the hunger remain? And is its return simply an exercise in nostalgia – or a timely reminder that we 21st-century types are just as in thrall to the idea of the conspiracy theory as previous generations?

In the best traditions of the Big Secret, I’ll have to kill you if I tell you. Instead, here’s psychologist Jan-Willem van Prooijen of Amsterdam’s Free University, who spent six years studying conspiracy theories and their adherents and published his findings in the journal, Applied Cognitive Psychology in August 2015.

“There are no doubt cultural variables influencing it,” he said. “But the essence of conspiracy theorising is, I think, universal in human beings.”

So it’s hard-wired into us. That said, van Prooijen found that belief in conspiracy theories waxes and wanes as people react to outside events such as, say, the turn of the Millennium, the 9/11 attacks or – pertinent to the return of The X-Files – the economic crisis of 2008.

And the more out of control people feel, the more they try to make sense of things by imposing an over-arching narrative and seeking an under-lying reason, even if that reason is malign. Or just downright bonkers. In van Prooijen’s words, these people end up trying to “connect dots that aren’t necessarily connected in reality”.

This is human nature, of course. Why have our Bronze Age crops failed? Because we displeased the Gods. Why is our late 19th-century social order crumbling? It’s the fault of the Jews, and here’s the anti-semitic and fabricated text of The Protocols Of The Elders Of Zion to prove it. Why are the polar ice caps melting? Because the Zylons are firing heat rays from behind their off-world cloaking device, dummy.

Van Prooijen also found that the belief in one conspiracy theory tends to lead to belief in others. “The more that people feared the millennium bug in 1999, the more they were inclined to believe in other conspiracy theories, ranging from Kennedy to the government hiding evidence of the existence of UFOs,” he said.

And his solution? “We found that if you give people a feeling of control, then they are less inclined to believe those conspiracy theories. Giving people a sense of control can make them less suspicious over governmental operations.”

Talking of government, “cryptocracy” is another word the conspiracy theorists love. It refers to what’s sometimes known as a “shadow government”, an unelected group of powerful individuals controlling the elected ones in which we (foolishly they say) place our faith. Transmitted into laws and statutes, the group’s wishes are thereby given a veneer of democratic legitimacy. That’s the theory, anyway. The Syndicate is a kind of cryptocracy and so is the Special Executive for Counterintelligence, Terrorism, Revenge and Extortion – or SPECTRE, as Ian Fleming christened it in his 1961 novel Thunderball. On ice since 1971’s Diamonds Are Forever, the Bond producers dusted it down and gave it a starring role in 007’s most recent film outing, more proof that our decade is as susceptible to a belief in conspiracies and secret organisations as any other.

Of course The Syndicate and SPECTRE are fictitious. Probably, anyway. Other organisations which some think meet the criteria for a cryptocracy are very real, however. One such is the Bilderberg Group. Established in 1954, it meets annually in private and has a membership of around 150, made up mostly of politicians, financiers and industrialists.

Its aim is to “foster dialogue between Europe and North America”, and to act as “a forum for informal discussions about megatrends and major issues facing the world”. The meetings are held under strict rules, which state that “participants are free to use the information received, but neither the identity nor the affiliation of the speaker(s) nor of any other participant may be revealed”. It’s easy to see why so much rumour swirls around the group, and why none of it is good.

So much for the puppet masters, what about the puppets – or “patsies” as they’re known? The word comes courtesy of the man embroiled in one of the 20th century’s greatest conspiracy theories, the assassination of President John F Kennedy in Dallas on November 22, 1963.

At 7.55pm on the following day, killer Lee Harvey Oswald is supposed to have uttered the words: “I’m just a patsy.” The claim, recorded in the notebook of journalist Seth Kantor, is one of the few verbatim statements we have as the Dallas police didn’t record their 12 hours of interviews with him. But what did Oswald mean? Well, 53 years on, the theories are legion, with everyone from the Mafia to the CIA to the KGB fingered as the shadowy agency which used him as its “patsy”. Since then the word has also been ascribed retrospectively to everyone from Guy Fawkes to Gavrilo Princip, the Bosnian Serb whose assassination of Archduke Franz Ferdinand started the First World War.

There’s plenty more in the conspiracy theorists’ lexicon. “False flags” is a favourite, used to describe an attempt to pin the blame for a particular action on somebody else. Another popular term is “crisis actor”, used to describe professional actors employed as supposedly innocent bystanders. Again, the purpose is to confuse and misdirect. The trouble with rolling our eyes at conspiracy theorists is that there are actually some real conspiracies and real cover-ups out there.

Watergate was one, something The Washington Post knows all about. The Iran-Contra Affair of the 1980s was another. And, though the Warren Commission into the killing of John F Kennedy ruled that Lee Harvey Oswald acted alone, a 1979 review by the House Select Committee on Assassinations determined that an unknown second assassin had shot and missed, and that Kennedy “was probably assassinated as a result of a conspiracy”.

When The X-Files first aired in September 1993, it portrayed a world where phone calls were made at desks or in kiosks, a tweet was something a bird did and if you used an eye pad it was to cure conjunctivitis. Today, all that has changed. A vital (and not altogether welcome) addition to the world of conspiracy theories is the internet and, in particular, social media platforms such as Twitter, Facebook and the many other sites which proliferate in China and the Middle East. Here, rumour spreads like wildfire, often accompanied by images whose authenticity can never be verified but which lend a kind of veracity to even the most outlandish claims.

The most recent example is the Paris attacks carried out by gunmen linked to Islamic State. Or, if you believe some of the theories being propagated in the immediate aftermath, carried out by the Americans, the French and the Israelis acting in concert in a “false flag” operation intended either to “lock down” the city ahead of a climate summit or give the French an excuse to close their borders against refugees. Meanwhile, within days of the 2012 Sandy Hook school shootings in Connecticut which took the lives of 20 schoolchildren and six teachers, there were internet claims of “crisis actors” in play there, and social media was awash with conspiracy theories. It even prompted an editorial on the subject in right-leaning newspaper The Washington Times.

“Such theories flourish in a society where people look for simplistic, easy answers as a response to complex, tragic situations,” the paper wrote. “The theories thrive in a culture that continues to be dumbed down to avoid acknowledging the unpleasant reality that evil exists. It was an evil man who took the lives of the schoolchildren at Sandy Hook. There can be no solution to the problem that does not start from this truth.”

But unfortunately, even that word “truth” is lexicological terrain to be argued about and fought over. For most of us it means applying rationality to events. For the conspiracy theorists, who often describe themselves as “Truthers”, it’s a self-describing badge of honour. And for Chris Carter, the blurred edges between its subjective and objective qualities, make it perfect for The X-Files’s famous strapline: “The Truth Is Out There”. Better, perhaps, to say ‘the truths’ are out there: many, varied and often competing.

But while we can guess at the truths Fox Mulder and his ilk believe in – that aliens exist, The Syndicate is real, the moon landings were faked, and Elvis runs a deli in Rapture, Indiana – the man who plays him is notably less convinced. So let’s end with David Duchovny’s take on shadow governments, cryptocracies, cover-ups, “crisis actors”, “false flags” and all those other conspiracy theory favourites. “People can’t keep secrets. I’ve never known anybody, not one person, to keep a secret,” he says. “Somebody talks. Somebody along the way opens their mouth. There are too many people, too many secrets to keep. It’s not human nature. I don’t believe in it.”

True? You decide.

The X-Files begins tomorrow on Channel 5 (9pm)