The reason why 2001: A Space Odyssey still fascinates audience cannot be ascribed wholly to the film's outstanding special effects, which continue to convince over thirty years after its release – a major achievement for a science-fiction movie made before the first Moon landing.

The less obvious draw, which compels the picture's devotees to return to this somewhat ponderous epic again and again, is that it is almost impossible to decide whether director Stanley Kubrick is presenting us with a vision of heaven or hell.

Take the evidence for an optimistic interpretation: at 'the dawn of man', a group of proto-humans huddle in the African savannah, shuddering in fear as feral cats patrol the night. The appearance of the Monolith, a featureless black plinth, literally acts as a deus ex machina – in an echo of the Biblical story, those who touch it attain the power of reason; in other words, they become human.

In one of the most audacious cuts in cinematic history, a tool – a piece of bone – is hurled into the sky by an apeman, and the revolving object resolves itself into a satellite in earth orbit. Now we are in 2001, and to the soothing cadences of The Blue Danube, we watch a Pan Am shuttle gently waltz with a wheeling space station (one considerably more impressive than the assemblage currently taking shape above our heads). It seems that humankind in the new millennium has achieved a perfect synthesis of high culture and high tech.

Then again… the tool thrown in the air is in fact a weapon used to stave in the head of an opponent from another tribe. The satellite into which it evolves is a floating weapons platform. Despite the classical music and sophisticated hardware, we still have much in common with the violent creatures from prehistory. It appears that reason and aggression go hand-in-hand.

The symbiosis is alluded to while the sole passenger of the Pan Am shuttle, Dr Heywood Floyd, is en route to the Moon to lead a team investigating the discovery of an alien artefact (the Monolith). On the station, he meets a group of Russian scientists who inquire about why an American lunar base has been sealed off. Although the exchange is conducted with polite formality, there is a whiff of the tribes clashing on the African plains three million years previously. Instead of cudgels, nuclear weapons operated by remote control buttress the stances of the cordial Cold War scientists. (We can be thankful that Pan American was not the only institution that failed to make it into the 21st century.)