The word "philosophical" rarely makes it on to movie posters. Perhaps philosophy's tendency to conjure up unseductive images of reclusive professors scratching their craniums and pondering their own existence is to blame. And yet, complex philosophical ideas are common in film - and not just on the arthouse circuit.
The newly released movie The Adjustment Bureau, featuring Matt Damon and Emily Blunt, is just one example of a Hollywood picture that embraces philosophy. The story sees Damon's character - a successful politician - fall for a free-spirited dancer after a chance meeting. But the pair's attempts to be together are constantly thwarted by a group of mysterious men in hats, who have decided that the couple's love is "not part of the plan". In the world of The Adjustment Bureau, choice is an illusion and fate is pre-ordained.
The movie - an exploration of the age-old debate about free will versus determinism - wears its intellectual credentials on its sleeve.
Here is a guide to some of the most explicitly philosophical films ever made and the grand ideas that inspired them.
Metropolis (1927) ... and Marx's idea of class conflict
Fritz Lang's silent classic Metropolis is the story of a futuristic dystopia, inhabited by two very different classes of people. Those who reside in the city's giant skyscrapers live a frivolous, bourgeois lifestyle, while the others are consigned to the bowels of the city, where they endure backbreaking labour. Before long, the ingrained inequality leads to the smashing of machinery by the workers and the entire edifice comes crashing to the ground - the whole thing reads like the pages of the Communist Manifesto.
"Metropolis is a Marxist love story, because the salvation in the film comes when a member of the bourgeois class and one of the workers fall in love," says Dr David Sorfa, the editor of the academic journal Film-Philosophy. "Although the film depicts class struggle it doesn't necessarily argue for it, but it does show that inequality can be overcome by ending the kind of rigid segregation that Marx described."
Last Year in Marienbad (1961) ... and Sartre's existential bad faith
In the surreal and often baffling world of Alain Resnais's film Last Year in Marienbad, the well-dressed guests at a party in a French château pass the time by discussing fashion and playing games. One man tells a woman that they met the year before in Marienbad and believes she is waiting for him, but she insists they have never met. The party's petty-minded attendees appear to be locked into an inescapable time loop where no choice really matters and history never existed.
It can be seen as a depiction of Jean-Paul Sartre's concept of "bad faith", the cardinal sin of existentialism.
"That film is about having no idea about what informs your choices and being so existentially empty that you almost don't care about what's right or wrong," says Sorfa. "It was a comment on the state of bourgeois living in France at the time."
Blade Runner (1982) ... and personal identity
Based on a story by Philip K Dick (like The Adjustment Bureau), Ridley Scott's paranoid future-noir sees a retired law enforcer (Harrison Ford) enlisted to hunt and kill four rogue "replicants".
Used for slave labour, the replicants are almost indistinguishable from humans physically and emotionally and are therefore almost impossible to identify. As well as posing the philosophical question of what exactly defines humanity, Blade Runner asks whether memory and experience can be trusted in a world where memories can be implanted.
"The film argues that humans are as much machines as machines are," says Sorfa. "Therefore, being a replicant shouldn't mean receiving less sympathy that a natural human subject. Once again, like Metropolis and The Adjustment Bureau, love is the thing that breaks the programming."
Crimes and Misdemeanors (1989) ... and moral relativism
In Woody Allen's black comedy, a successful ophthalmologist (Martin Landau) sets in motion a chain of events that result in a hitman killing his mistress before she can reveal details of their affair to his wife. Far from evil deeds begetting evil outcomes, his life and those of many others improve dramatically as a result of the murder.
However, the protagonist's relativistic view of morality differs greatly from that of a blind rabbi he is treating, for whom moral absolutes do exist. "Allen asks what it means to act 'well'," says Sorfa. "The film makes the point that what is 'good' or 'bad' depends on the ethical system to which you subscribe and ethics can change dramatically between individuals and over time."
Groundhog Day (1993) ... and stoicism
The comedy sees Bull Murray's self-consumed TV weatherman forced to relive the same single day again and again, while everyone else believes they are experiencing it for the first time. Knowing that his actions count for little, he first becomes hedonistic, then depressed and finally suicidal, killing himself many times over. He also struggles to win the heart of his female colleague (Andie MacDowell) - despite an almost infinite number of attempts to woo her - until he finally forgets his own selfish desires and acts for the good of others. Stoicism, a school of Hellenistic philosophy from the 3rd century BC, suggests that virtuous actions lead to happiness and that freedom is secured not by the fulfilling of desires, but by their removal.
"It's almost like a philosophical algorithm," says Sorfa. "If what makes you happy is to fulfil your desires, the easiest way of achieving that is to scale down your desires. The difficulty with that is that we are not really in control of our desires."
The Matrix (1999) ... and Cartesian scepticism
Although not the first to deal with the idea, the Wachowski brothers' action film is perhaps the best-known example of the French philosopher René Descartes's notion of doubt in the movies. The story sets up a world in which humans believe they are experiencing a reality that resembles ours, but are in fact sharing a collective illusion while their physical bodies are being used as power cells to feed the very machines that hold them captive. Almost 400 years before the film, Descartes asserted that sensory experience, the primary source of knowledge, is capable of being tricked and therefore must be doubted.
"The contemporary philosopher Slavoj Žižek said he had the good fortune of watching The Matrix next to the ideal cinema goer for the film - namely, an idiot. The film presents Descartes's idea so simply and explicitly that anyone is capable of grasping it," says Sorfa
Eternal Sunshine of the Spotless Mind (2004) ... and Nietzsche's eternal recurrence
Michel Gondry and Charlie Kaufman's mind-bending romance sees a lovelorn couple (Jim Carrey and Kate Winslet) repeatedly erasing their memories of each other after finding their break-ups too difficult to bear. But erasing memories is the easy part, neither can change the part of themselves that made them fall in love in the first place.
Because they are unable to change their actions, the pair continue to fall for each other. In the late 19th century, the German philosopher Friedrich Nietzsche postulated the theory that, if the universe is infinite, our world will occur identically again an infinite number of times. While he admitted this is "horrifying and paralysing" it should also be embraced as the ultimate affirmation of life, he argued.
"The characters in the film seem to be destined to return to each other because the decisions they make to erase their memories don't fundamentally change them," says Sorfa.