It’s not only Sydney. Just as a tree’s age and context are legible in its annular rings, so a city’s age and determinants are legible in the density of its core and its subsequent growth-rings. Sydney was luckier than Auckland, say, or Houston, in having crystallised, as it were, that much earlier, before the car blew it all apart. But as Haskell notes, cities everywhere – including the Parises and Florences – are now ringed by medium and low-density sprawl every bit as relentless and hideous as ours.

This, though – and the fact that when Sydneysiders hear the word ”density” those beige boxes and redbrick walk-ups are what they see – tells us more about 20th century arrogance than about density per se.

That’s scandalous enough, but the real jaw-dropper is that architecture wants to go again, and is reviving modernism holus bolus. Pick up any mag and you’ll be hit by some odd-angled, flat-topped, board-form concrete house; eaveless, shadeless, shadowless, sill-less. As though water no longer ran downhill, glass no longer trapped heat, people no longer delighted in grace, breeze or transition.

The particular house I’m slagging is the Fosc House in Chile, but it could be any one of hundreds that have been darlinged by the design mags over recent months, including several in this country. Modernism is not only back, it’s back unrethought, unreconstituted, unrepentant. How can sentient professionals be so dumb?

It’s sometimes tempting to think this stuff trivial, and in a way it is. But the density issue illustrates just how pivotal architecture will be in determining the future of the species.

In November 2008, while the world’s eyes were crossed on Obama and the Intergovernmental Panel on Climate Change, humanity passed an important milestone. Thenceforth, more than half of us live in cities. How those cities are shaped – and how lovely they are – will largely determine our wellbeing and even our survival.

Again as Haskell notes, the European city-cores we admire are distinguished by “the type of architecture that ensures inner-city living can be a pleasure”. Can this be so hard to do? Well no. It’s not hard. It’s just that pleasure – other than the architect’s pleasure at making the glossy front covers – hasn’t been on architecture’s critical path for some time. And now, making matters worse, we’ve allowed a system to take root that means it can never be reinstated.

There are several factors here: the way modernism played – nay, danced – into the hands of the profiteers, the way successive governments sold out to these same profiteers in the fiasco we call ”planning”, and the way virtually all city-building is now done by publicly-listed developers whose shareholders actively eschew superfluities like delight (ours).

So just when it matters most, environmentally, that we get our cities right; just when city living has become a majority interest and just when democracy ensures that our cities cannot be shaped by fiat but only by desire; at this precise moment we find ourselves saddled with a building procurement system that all but prohibits the building of pleasurable cities.

Cities are greener than suburbs. No question, and in countless ways. Edward Glaeser’s Harvard study compared city and suburban emissions from driving, public transport, heating, electricity across 46 US cities. His report is on the net. Check it out. There are also savings in construction, infrastructure, farmland, forest and food transport. But to save us, cities have to be more than green. They have to make us want them.

So it’s heartening that Glaeser makes San Francisco America’s greenest, since it is also lovely; light, tight timber terraces and apartments, medium and high density, rent-controlled and in general, height-controlled. But its big achievement – and this is hard – is accommodating the car without losing its picturesqueness.

The only Sydney example that comes close is Surry Hills’s Moore Park Gardens. Designed by Alan Jack + Cottier back in the ’90s, MPG provides 560 apartments in three to 20 storeys on 2.6 hectares. By our standards that’s pretty dense.

But it doesn’t feel it. With its sophisticated and varied composition, myriad walkways, luscious planting, parks, pools and established delis, it creates not just a community, but a genuine middle-class chic. This is seriously rare. The disgrace is that in the last decade’s huge medium-density boom, nothing has come even close.

For me the acid test is this. Can I imagine someone reading Kant in there, hammering out the next Dada, writing the next Houellebecq, making the next Star Wars? Answer, yes, actually. No trouble.