In the beginning, Western philosophy was profoundly mistrustful of the written word. Socrates was the first thinker to move beyond poetry and sophistry to what we now consider philosophy, yet his teaching was purely oral. To think with Socrates meant having dinner with him, walking home from a festival with him, or collaring him in the marketplace; he made philosophy an encounter and an experience, but not a text. That was left for Plato, his disciple, who used writing to preserve Socratic dialogues for future generations. Yet Plato himself feared that, by transforming philosophy into what it remains to this day – a matter of writing and reading, not hearing and talking – he was betraying its essence.

In his “Phaedrus,” Plato records the myth of Theuth, or Thoth, the god whom the Egyptians credited with the invention of writing. Theuth urged Thamus, the king of Egypt, to teach his people how to write, claiming: “Here is an accomplishment, my lord the king, which will improve both the wisdom and the memory of the Egyptians.” But Thamus turned this boast on its head: “You who are the father of writing,” he insisted, “have out of fondness for your offspring attributed to it quite the opposite of its real function. Those who acquire it will cease to exercise their memory and become forgetful. … And as for wisdom, your pupils will have the reputation for it without the reality; they will receive a quantity of information without proper instruction, and in consequence be thought very knowledgeable when they are for the most part quite ignorant.”

Today, for the first time since Plato, we are entering an era when writing may once again lose its place at the center of intellectual life. But we are not going back to the world of Socrates, where genuine thinking and teaching flourished in face-to-face encounters. In the age of television and the Internet, we are not returning to the preliterate, but descending into the postliterate. Writing may have been merely a trace of the genuine experience of philosophy, but what will happen when even the trace disappears, leaving nothing but images – the images that, to Plato, were the most transitory and untrustworthy of all things in this world of change? Can thinking take place in a visual medium?

That is the question posed, quite self-consciously, by “The Ister,” a fascinating new documentary that made its debut in 2004 and has been slowly making the rounds of film festivals, art-house cinemas, and academic conferences. (Though it is available on DVD in England and Australia, screenings in the United States must be arranged through Brooklyn-based First Run Films.) “The Ister,” shot on digital video by a pair of Australian graduate students, Daniel Ross and David Barison, is a nonfiction film but not a documentary, at least not in the usual sense: For while it does document many things, places, and people, its central purpose is not to record an event but to provide an experience – “not merely to illustrate but to provoke thought,” in Mr. Ross’s words. This high ambition makes “The Ister,” which runs for three hours and took some five years to produce, an important test of whether the philosophical impulse can survive in the new world of images.

Plato’s myth of Theuth offers a perfect route into the questions raised by “The Ister.” For the major subject of the film is the power and danger of technology, of which Theuth, like the Greek Hermes, was the patron deity. And the filmmakers’ major interlocutor, the philosopher around whom the film cautiously circles, is Martin Heidegger, whose suspicion of technology went hand in hand with a powerful challenge to conventional ways of writing and talking about ideas.

The film takes its name from a poem by Friedrich Holderlin, the late-18th century German Romantic, whose hymn to the Danube River called it by its ancient Greek name, “the Ister.” More specifically, the film is inspired by a lecture course on “The Ister” that Heidegger gave in 1942,one of many he devoted to Holderlin’s poetry. The formal structure of the film is simple but fertile: Camera in hand, Messrs. Ross and Barison (who never appear onscreen) follow the course of the Danube, from its mouth on the Black Sea back to its source in Germany.

Their travelogue pays careful attention to the bridges and ships and cities they discover along the way, thus providing an illustration of Heidegger’s major theme – man’s imposition on Nature, in all its destructive necessity. Messrs. Ross and Barison produce several lovely tableaux – of rivers, mountains, forests – but the visual strength of the film lies not in beauty but in clever juxtaposition.

In Romania the filmmakers visit the ruins of the bridge across which Trajan’s armies marched into Dacia; in Yugoslavia they show the bridge at Novi Sad, destroyed by the NATO bombing campaign in 1999; in Hungary, they find a bridge at Dunafoldvar which was attacked by the invading Soviets in 1956. Over the course of the film, and with very little nudging by the filmmakers, the figure of the bridge comes to bear the full weight of Heidegger’s critique of technology: As a human intervention into Nature, it is both essential to life and bound up with violence and death.

The bridges on the Danube are products of what Heidegger, in his essay “The Question Concerning Technology,” called “enframing” – a way of thinking that makes Nature subordinate to human ends. In that essay, Heidegger showed how his thought about technology relates to his thought about poetry, and specifically the poetry of Holderlin. Taking up another one of the poet’s river-odes, “The Rhine,” Heidegger contrasts “‘The Rhine,’ as dammed up into the power works, and ‘The Rhine,’ as uttered by the artwork, in the Holderlin’s hymn of that name.” The contrast speaks volumes about Heidegger’s sense of the betrayal of Nature – its reticence and mystery, the essential Being that Holderlin invokes – by technology, which turns it into merely an exploitable resource.

To the great credit of Messrs. Ross and Barison, however, they do not stop at simply illustrating Heidegger’s thought; they allow it to be challenged, trusting the viewer to take part in a series of complex philosophical debates. These are expounded in the interviews that make up the intellectual pith of “The Ister,” a series of talks with three French philosophers – Bernard Stiegler, Jean-Luc Nancy, and Philippe Lacoue-Labarthe. (There is also an interview, much less compelling, with the pompous filmmaker Hans-Jurgen Syberberg.) Editing their questions out almost completely, Messrs. Ross and Barison allow these thinkers to elaborate on their own disagreements with Heidegger’s views on technology – disagreements that spring from a fundamental indebtedness and respect. Thanks to the informality of the settings – we see Mr. Stiegler quieting his dog and blowing out candles at his birthday party – the men become more than talking heads; we take in some of their eccentricities along with their ideas.

As the filmmakers’ itinerary reaches Germany, “The Ister” turns to confront another, more controversial aspect of Heidegger: his embrace of Nazism, and his seeming refusal, even after the war, to acknowledge the magnitude of its evil. His lecture on the Holderlin poem, after all, took place at the height of the Nazi period and contained admiring references to “National Socialism and its historical uniqueness.” Mr. Lacoue-Labarthe devotes most of his screen time to explaining Heidegger’s infamous equation of the concentration camps with “motorized agriculture,” and elaborates a powerful critique of Heidegger’s view of history. And Mr. Stiegler, the most charismatic figure in the film, convincingly challenges Heidegger’s bleak view of technology, arguing that were it not for technology – above all, that of writing – we could not live historically at all.

This lesson, too, is implicit in Holderlin’s poetry; as he writes in “The Ister”:

But the rock needs incisions
And the earth needs furrows,
Would be desolate else, unabiding.

“The Ister,” then, not only contains a humanistic defense of technology; it is itself part of that defense, using one of the newest media to address some of the most ancient questions. The film cannot by itself serve as an introduction to Heidegger’s thought, and much is inevitably simplified and taken for granted. To fully appreciate what Messrs. Ross and Barison are up to, it is helpful to have already spent some time with Heidegger’s work. But the fact that it could be made, and even distributed, is heartening testimony to the potential of a usually barren medium.