In the autumn of 1980, I learned to overcome one of mankind’s greatest fears. Conquering it was a matter of moving silently across cornfield stubble in the dead of night, lying in wait at the edge of a copse for several hours in pitch dark, and storming an old castle long after dusk. When I undertook the Commando training course of the Royal Marines, I learned that night was my friend, not my fear.

It’s one of the big disadvantages of being human, I guess. Our cat, for all her indecisiveness and paroxysmally odd behaviour, can leap from our bed when the light is off, and see almost as well as she does in daylight. Yet when we get out of bed to go for a pee at 0400, we can’t see a thing without turning a light on.

So for many of us, darkness is the world of the unseen and unknown, a world of eerie sounds and doings, when the werewolves roam, and harmless bats turn the bold into blancmange. There might sometimes – as in Stuart Pearson Wright’s painting below – be a touch of frisson, but when it comes down to it, we are deeply scared of the unknown and alien.

Though many of us now enjoy a world without borders, discourse without prejudice, and unprecedented global cultural richness, we are the few. Most people still stick around their home town, talk with others of their own colour, caste, and creed, and long for their own insular comforts. For them, most things foreign are like the night. All they want to do is turn on the light, and reassure themselves that their world order is as it always has been.

We are now seeing those primaeval and deep-seated fears brought to the surface. In the UK during our recent referendum campaign, in the US Presidential Primaries, throughout much of Europe, there are public figures who are turning over people’s inner fears, and preying on them. Expressions of xenophobia abound. Some have been so unashamed as to be outrageous: one of the posters used in the UK’s referendum campaign was a modernised version of one used by the Nazi party during the 1930s, and by any standards violated national and moral law.

Xenophobic propaganda is equally happy to assert blatant lies, and to propound the logically impossible. Senator Ted Cruz’s “We must keep the internet free”, seen here, claims that only by keeping it under US control can it be protected from the harm that those evil foreigners will do to it, for example.

Rising fear opens up every nasty little crack that we have been trying to heal over. Friends and colleagues are dragged into arguments which they would previously never have gone near. We’re forced to take sides, as if in some childhood game of cowboys and Indians. Only now it’s for real: the blood is not theatrical but someone’s life, and the guns kill people.

Just like our fear of the dark, the only answer is to conquer that fear, and to help others conquer theirs. We need to expose propaganda, and those who succeed on its back, for what it is. When accused of being part of ‘project fear’, we must show that it is actually they who are exploiting fear and trashing the rational. When they cry for freedom, we must show how they are actually oppressing. For it is the propagandist’s style to accuse their opponents of their own greatest faults: it seizes the sound-byte, and stifles thought about meaning or truth.

We must show how reason, knowledge, wisdom, and the ideals of mankind can turn these fears around, and bring us together, not cleave us apart.