The fall of the Berlin Wall 20 years ago  is rightly taken as a symbol, not just of the ending of an oppressive regime, but of the dismantling of a monstrous barrier between families, communities and societies. It also marked the moment when a new, more "borderless" world seemed upon us.
It is good that we can celebrate the demise of that ugly institution this week. But we should bear in mind as we do so that, around the world, there remain many walls that still keep loved ones apart, workers from their places of work, and communities from joining together.
In the early 1990s, it was widely felt in academic and policymaking circles that, after communism, the "end of history " was upon us. As the internet hooked up those with access to computers, as air travel became ever cheaper, and as the increasing liquidity of capital saw more wealth moved around the globe than ever before, this became -- through the dogma of globalisation -- the prevailing view in the west.
But, for many, the idea of a borderless world was never much more than a convenient phrase, used to justify an increasingly aggressive capitalism. And post-9/11, it has certainly become much harder to maintain the view that we live in a hyper-globalised world where international movement is as easy as waving a passport at the border.
Even for those with the luxury of travelling wherever and whenever they want, the lengthening queues at the airport and increasingly intrusive identity checks are emblematic of the constraints that have been set on this freedom. More importantly, for others, the post-9/11 world has brought the introduction of new borders and divides every bit as unbridgeable as the Berlin Wall.
This is obvious in places where today's Berlin Walls take an equally physical and imperious form (as in the case of the Israel-West Bank barrier, for example). There the border is every bit as ideologically invested as the East-West German border was, and the sufferance caused every bit as stark. It is less obvious, but no less important, however, where the borders between people are enforced by more subtle, insinuating forms.
The plethora of biometric profiling techniques and border-tightening measures that nation states have erected over recent years in the name of national security is a case in point. On the US-Canadian border, for example, where the NEXUS system is used to keep perfectly legitimate but economically less desirable migrants out of a country in order to cherry-pick the workforce. Or as in the UK, where the idea of "hardening" the border was last week floated by the chairman of the parliamentary intelligence and security committee, Kim Howells, as an alternative to stepping up the war in Afghanistan. These border controls may be raised in the name of national security, but one only needs to stand in line at customs to appreciate how their operation is so readily inflected by class, race and ethnicity.
Such developments are the product not of a borderless world, but of what some call "gated globalism": a world of borders policed in the name of underexamined aims (such as "security"), where freedom of movement for some comes at the price of greater restrictions for others. These are the actually existing freedoms of today's neoliberalised boundaries, their effects far less visible than those of a wall, but their implications for many no less damaging.
So perhaps less has changed in the course of two decades than we might like to think. The idea of a borderless world was an illusion of the excessive western triumphalism of the 1990s. Today it remains an illusion, but because of excessive western anxiety. The figure of the terrorist has replaced the communist "other" and the discourse of security replaces the dogma of one-size-fits-all democracy. The only difference, in fact, is that those technological developments that promised the death of geography in the 1990s now herald its return. For those whose ability to move is restricted on account of where they come from, or beccause of what they believe, today's borders are indeed every bit as impregnable as the Berlin Wall.