To appreciate the cultural impact of Peter Weir’s 1989 coming-of-age classic, Dead Poets Society, one need only note that for a whole generation the line “O Captain! My Captain!” evokes not the poem from which it originated – Walt Whitman’s 1865 elegy to the then recently assassinated US president Abraham Lincoln – but actor Robin Williams.

Weir’s film, about an enigmatic and unconventional teacher and the students whose lives he turns upside down, celebrates its 30th birthday this month. Its appropriation of Whitman’s poetry is a testament to its enduring legacy – and to one scene in particular, seared into the public consciousness.

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Who could forget that rousing finale, when students of Williams’ John Keating salute their think-outside-the-box teacher by standing on top of their desks and proclaiming “O Captain! My Captain!”? This act of rebellion, replete with a villainous substitute scrambling for control of the classroom, distills the film’s gently anti-establishment messages into a single, meme-able moment. A core theme made literal: contemplate life from a different perspective.

Facebook Twitter Pinterest Members of the Dead Poets Society gather. Photograph: Touchstone/Kobal/REX/Shutterstock

This moment takes place in the shadow of tragedy, after the heads of a conservative private school unfairly blame Keating for the suicide of one of his students. When, in August 2014, the hashtag #ocaptainmycaptain went viral for the first time (the film was pre-social media and so, of course, was Whitman’s poem) the context was again tragic, following the death by suicide of Williams himself.

There is something beautiful and yet profoundly melancholic about this cycle: poetry celebrated through film, then film celebrated through social media, with real-life tragedy and great outpourings of grief and affection at the core of it all. Poetry purists might turn their nose up at the idea that some people, maybe even most people, now associate Whitman’s verse first and foremost with a movie rather than a poem. But there’s a lovely synchronicity here between real-life and Keating’s objectives, given the teacher’s passion for finding ways to keep poetry relevant and exciting for younger generations.

Facebook Twitter Pinterest Robin Williams as the enigmatic and unconventional teacher John Keating in Dead Poets Society. Photograph: Touchstone/Kobal/REX/Shutterstock

Dead Poets Society was a hit at the box office and collected plenty of kudos – including a Bafta award for best film and an Academy award for best original screenplay (it was nominated for three others: best picture, best actor and best director). It has grown in stature over the years, spawning a spin-off stage play and novel, as well as being a common text on school curriculums and in lists of inspirational movies, such as this from the American Film Institute.

It is one of those films that means different things at different points in your life. As a high school student I remember feeling inspired by it in the obvious ways: to appreciate the creation and consumption of art, and, in my case, to continue pursuing a passion for writing. As a much older adult, Dead Poets Society affects me more as a story about the qualities of inspiration itself: the potential for our words and actions to move and motivate people around us.

Like Weir’s other film based in and around an exclusive private school, the more enigmatic Picnic at Hanging Rock, education is viewed as a pivotal but dangerous experience. The capacity for young people to find themselves and flourish is countered by the chilling potential for them to destroy themselves, or to be destroyed by a large and at times brutal world.

Facebook Twitter Pinterest Robert Sean Leonard as one of John Keating’s students in Dead Poets Society. Photograph: Moviestore/REX/Shutterstock

Most of the film is dramatically obvious, at times borderline simplistic and twee, with its gentle “think differently, dammit!” contrarianism. But it’s easy to forget the nuance. Before I watched Dead Poets again, for example, some time in my 20s, I vividly remembered the “O Captain! My Captain!” scene as showing the entire class rise up and stand on their desks, united in honour of their teacher. The emotionally wounded Keating leaves a restored man, buoyed by their full support.

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I had misremembered this crucial moment. Half the class don’t actually move from their seats or show any recognition of Keating at all. They stare straight ahead, faces as lifeless as mannequins, and ignore him, waiting for the moment to end. How would these boys, I wonder, recall this event decades later? Would they look back and regret doing nothing? Would they feel shame?

I like to think they would. This fits with the film’s core themes: about grabbing life by the horns, being bold and brave and kind and virtuous while we have the opportunity. These sentiments can be summarised using two words, which, like “O Captain! My Captain!”, many younger viewers were made aware of for the first time by watching Dead Poets Society: “carpe diem.”

Or as Keating puts it: “Carpe diem. Seize the day, boys. Make your lives extraordinary.”