The poster in my classroom, too, revealed a movement impossible for the naked eye to perceive: from lower primate to higher, from Neanderthal to human, and - this last transition was so compressed as to be absent altogether - from the human to the European. These still figures gave us an 'optical unconscious' of a political context, the context of progress and European science and humanism. Here, too, Benjamin has something to say. In a late essay, 'Theses on the Philosophy of History', he stated: 'The concept of the historical progress of mankind cannot be sundered from the concept of its progression through a homogeneous, empty time.'

'Homogeneous' and 'empty' are curious adjectives for 'time': they are more readily associated with space and spatial configuration. Certain landscapes glimpsed from a motorway, or the look of a motorway itself, might be described as dull and 'homogeneous'; streets and rooms might be 'empty'. My mentioning motorways isn't fortuitous. When Benjamin was formulating his thoughts on progress and history, and writing this essay in 1940, the year he killed himself, Hitler, besides carrying out his elaborate plans for the Jews in Germany, was implementing another huge and devastating project: the Autobahn. The project, intended both to connect one part of Germany to another and to colonise the landscape, was begun in the early 1930s; it's clear that Hitler's vision of the Autobahn is based on an idea of progress - 'progress' not only in the sense of movement between one place and another, but in the sense of science and civilisation. In India, in other parts of the so-called 'developing' world, even in present-day New York, London or Paris, it's impossible properly to experience 'homogeneous, empty time' because of the random, often maddeningly diverse allocation of space, human habitation and community. It is, however, possible to experience it on Western motorways and highways. Hitler was a literalist of this philosophy of space and movement: he wanted space to be 'homogeneous', or blond and European. Benjamin knew this first-hand; he was writing his 'Theses on the Philosophy of History' as a Jewish witness to Nazism and one of its potential victims. Hitler's anxiety and consternation at Jesse Owens's victory in the 100 metres at the Munich Olympics in 1936 came from his literalism of space, his investment in progress and linearity. That idea of space was at once reified and shattered when Owens reached the finishing line before the others.

Benjamin had been thinking of history in terms of space for a while; and, not too long before he wrote about 'homogeneous, empty time', he'd posited an alternative version of modernity and space in his descriptions of the flâneur, the Parisian arcades and 19th-century street life. The Parisian street constitutes Benjamin's critique of the Autobahn: just as the crowd, according to Benjamin, is 'present everywhere' in Baudelaire's work, and present so intrinsically that it's never directly described, the Autobahn is implicitly present, and refuted, in Benjamin's meditations on Paris. The flâneur, indeed, retards and parodies the idea of 'progress'. 'Around 1840 it was briefly fashionable to take turtles for a walk in the arcades,' Benjamin writes in a footnote to his 1939 essay on Baudelaire. 'The flâneurs liked to have the turtles set the pace for them. If they had had their way, progress would have been obliged to accommodate itself to this space. But this attitude did not prevail; Taylor, who popularised the watchword "Down with dawdling!", carried the day.' The flâneur views history subversively; he - and it is usually he - deliberately relocates its meanings, its hierarchies. As far back as 1929, Benjamin had explained why the flâneur had to be situated in Paris: