Michael Mehaffy - The New Modernity

The “modern” era of the last century and beyond -- the most productive and progressive epoch in human history -- is in an inexorable end-stage crisis. The last century's unbridled optimism about the rational progress of humanity has given way to a more sober understanding – for some a cynical despair -- about the limitations of human reason, and the insidious imperatives of technology. At the same time the reductionist science that has propelled the modern era is giving way to another, more advanced kind of science: one reflecting a new understanding of the complex adaptive structure of nature (including human nature) and a recognition of the environmental and cultural damage that the modern era has done. The “new science” – like the old science that preceded it – carries profound implications for the structure of technological culture and the patterns of life embodied in architecture. But cultural systems, and the architecture and built environment that shape and express them, are lagging behind. In an environment in which the old century of mechanics is giving way to a new century of biological complexity, it is time to ask deep questions about the implications for the architecture of human culture. The answers offer a surprisingly hopeful basis for a new and more humane “architecture of our time.”

I. The “Old Modernity” of Mechanical Science

II. The New Science of Complexity

III. Seven Properties of Complexity

¨ Network Structure

¨ Near Decomposability

¨ Fractal Geometry

¨ Adaptive Iteration

¨ Geometric Holism

¨ Structural Attractors

¨ Connective Symmetries

IV. The Architecture of Complexity

V. Towards a New Architecture of Life

VI. Notes

I. The “Old Modernity” of Mechanical Science

Modernism's alchemistic promise – to transform quantity into quality through abstraction and repetition – has been a failure, a hoax: magic that didn't work. Its ideas, aesthetics, strategies are finished. Together, all attempts to make a new beginning have only discredited the idea of a new beginning. A collective shame in the wake of this fiasco has left a massive crater in our understanding of modernity and modernization.

- Rem Koolhaas, “Whatever Happened to Urbanism?”

“The future” is mired in the past.

Around the world today an old chimera of modernity still holds us spellbound. Its rules and assumptions fuel our prodigious industry, our fashions, our vision of ourselves. It governs our pursuit of endlessly (not to say pointlessly) greater levels of prosperity and wealth. At a deeper level it lures us with its seductive promise of a final deliverance of humanity from the horrors of nature untamed. It is – or so we had desperately hoped -- the final achievement of the Enlightenment triumph of human reason.

But the foundation of this quest is crumbling all around us; the signs of its internal contradictions and fallacies are increasingly unmistakable. Today it has become an ironic parody of its own once-confident quest for advancement. And yet we remain prisoners of its spell, unable to see where to go next.

In architecture – the realm of art with the greatest impact upon living patterns – today’s “futuristic” jagged crystalline towers are not much different from set pieces from the 1924 movie Metropolis or the 1939 movie The Wizard of Oz. Skylines take on the quaint spaceship forms of Buck Rogers, or the dazzlingly wacky forms of an old theme park, complete with exploding fireworks. Interiors have returned to the uncomfortable fashion-victim minimalism of the 1960’s, complete with tacky plastic chairs and un-tacky price tags. Metropolises are still largely planned around passengers in speeding automobiles, whisking far out to suburbs of gleaming corporate office parks set far back from the road – all of it perfectly described (sans congestion, pollution and other dysfunctions) in the utopian drawings of almost a century ago.

These are but the superficial signs that the “modern” era of roughly the last century -- the most astonishingly productive and politically progressive epoch in human history -- is today in a deepening end-stage crisis.

Let us be clear about the triumphs achieved. This era, with roots stretching back to Newton and Descartes – and even deeper, into the rational idealism of Plato and even the nature of human thought itself -- has delivered breathtaking advancements for humanity. Its vast wealth has been fuelled by a revolution in science and mathematics, and in particular in our understanding of the structure of nature and the cosmos. Along with this, as a parallel and interactive phenomenon, has come an explosive revolution in technology, production, wealth, political liberalism, and the means of living.

Today we can fly, heal, dine, in a manner undreamt of by the richest kings of history. Some of us – members of the industrialised democracies, at least -- operate with unprecedented freedom from the oppressions of history. We should marvel indeed at this astonishing human achievement.

And yet we know there are costs. We know there is uncertainty, contradiction, danger. We struggle to see the next stage, and desperately try to rework the existing regime. Have we gone deeply enough? Are we hurtling toward the edge of a precipice?

Architecture has always had a unique place among the arts in shaping the structure of human life within nature. Often that singular responsibility has meant translating a new technological capability into a mode of living, thereby promoting and accelerating it. At the beginning of the last century, the architecture profession took the new transformation as a challenge to create such a new architecture: more rational, more scientific, more open and more advanced than what came before. Along with this was a corollary of political liberation from the old aristocracies and the old bourgeois authorities. We would see the final completion of the grand Enlightenment project.

And in the last century, there was indeed a great explosion of new forms and new ideas, in architecture and in all the arts – propelled by, and in some cases racing to catch up to, the new technological realities. The era was fuelled by a boundless optimism about the possibilities of a more genuine and more liberating human culture. The impetus to liberation reached new levels in the wake of the victory over fascism, and an eagerness to cement the final graduation of humanity from such atavist horrors.

There is no doubt that this period, continuing with variations to the present day, has been an exuberant, fascinating and deeply important phase of the history of architecture and the means of living – a grand experiment in the application of once-new scientific and technological ideas toward humane ends. It has been one of humanity’s great adventures. This author takes personal pleasure in having been a witness and participant in it.

But as we enter a new century the signs are unavoidable that the project is moribund and near collapse. The legacy of almost a century of this modernism, this radical attempt to accommodate the old industrial technology to a fine architecture and design, has been disorder, dysfunction, and a deep complicity in the global threat to life itself.

Amid the occasional remarkable pieces of fine minimalist art, the effect upon the many thousands of ordinary buildings, public spaces and artefacts, and upon the environment generally around the globe, has been nothing short of devastating. The worthy project of architecture to accommodate the new industrial reality, and to humanise it, has been a quixotic dream. The technocratic architecture has instead conspired with an increasingly shallow technocratic culture to dehumanise humanity, and nature itself.

We modernists have a lot to answer for.

Today the old modernist project is in a frantic, desperate search for renewal. And in this endeavour it is increasingly an embarrassing parody of itself – at one moment acknowledging its relegation to the status of corporate servant creating fashionable “junkspace,” at the next moment claiming to profound expression of the zeitgeist and sneering at the past, at still the next moment delving shamelessly back into its own retro-modernist version of “insipid nostalgia.”

Moreover, we do not seem to be able to break away. The more we try to transcend our old technocratic bonds with one wild damn thing after another, the more we seem trapped in their inescapable grasp. The more we try to make extravagant singular novelties, the more they all merge into an incoherent white noise of disordered structure.

We have lost the coherent environmental order and geometric richness that was once the birthright of the human race.

“Good riddance!” we may well say. We are liberated and enlightened; we are modernists. This is our satisfactory bargain with history, or at any rate our inexorable condition, our fate: to swim in a sea of disordered “complexity.” We cannot go home again.

But a curious dilemma then poses itself: how then to secure the theoretical basis of an increasingly antiquated “modernist” architectural art?

Perhaps through an ironic post-modernism we can still recover the symbol and meaning of our roots, while accommodating modern technologies and modern liberation from the oppressions of tradition? But we recoil in horror at the grotesquely out-scale, mechanically cartoonish forms of such symbolic expressions in a modern context. Something is creepily out of scale, out of out of place.

Perhaps a post-structural politics can inform our work? Then we can at least recognise the ways in which privileged elites impose their “narratives” on us, and we can “deconstruct” these impositions and thereby offer a cleansing art of liberation. But then we ourselves become privileged elites, imposing our own narratives upon cities on a massive scale. Moreover, we enter a philosophical hall of mirrors in which essential meaning itself is presumed socially constructed – in which, to use Derrida’s phrase, there is nothing outside the text. Then we find ourselves in a tangle of self-contradictory nihilism, in which the notion of externally-verifiable structure that must lie at the heart of credible science – the foundation of Enlightenment modernism – collapses into absurdity.¹

The truth (whether or not anybody constructs it thus) is that architecture has long been marginalized by the hegemony of a rampaging technocracy. Architects, caught in this Ellulian trap,² are no longer engaged deeply with the fabric of the culture, as that is now generated autonomously by technocratic imperatives. Thus they are relegated to the role of macro-sculptors, adding a layer of marketable style to the Empire’s New Clothes. That they themselves still celebrate this exalted position for grand artistry is a sign of the full extent of their neurotic accommodation.

The reality is that in most of the building acts throughout the culture, the irrelevance of architects and “designers” is almost total. They have become part of the entertainment machine, engaged with rendering their own simulacra of culture – no less than the “theme park nostalgia” they so eagerly attack. Thus are we all relegated to quarrelling with one another over our mutual forgeries.

And so modernism and its progeny remain no less mired in the past – the past of a hegemonic industrial technocracy -- trying ever more desperately to revive and reinvigorate a doomed project of naked apology. It has not yet understood that the problem cannot be solved at the level at which it was created.

The old modernity was largely a product of the old mechanical science. If there is indeed a “new science,” we may suspect that it implies a new understanding of nature and of human nature, and it will inexorably produce a new ordering of technological culture. We have scarcely begun to assess in any depth what that might truly mean.

II. The New Science of Complexity

As science has probed deeper into the mysteries of the universe, we have encountered a strange and wondrous truth. From galaxies to DNA to the nucleus of the atom to superstrings, we see that the universe is a vast assemblage of structures of energy in space and time. All of the characteristics we can experience, all of the complexities of life and beauty, are structures of smaller structural components. Though unfathomable in its immensity and intricacy, the universe is, in its essence, a geometric structure.

This structure is vast but far from chaotic. The precise relationships of its geometries are what make stars shine and flowers grow. All of the differences between a bacterium and a human being come down to tiny differences in the sequences of molecules of otherwise identical DNA, made from only four molecules. The structures of the universe are intricately ordered, but in a vastly complex way – and enormously, exceedingly difficult for the human mind to comprehend.

The history of science and technology is one of rough but improving approximations of these structures of the universe, and the geometries that order them. For example, the Euclidean plane gave way to the curved geometry of the surface of the earth, and later to the curved fabric of space-time itself. Similarly, the two-variable mathematics of Newtonian physics gave way to the statistical mathematics of probability, and, only recently, to the non-linear mathematics of organized complexity.

It is in the nature of scientific understanding – and indeed of all knowledge -- that at any given time we are not aware of the inaccuracies of our current model of reality. We do not know what we do not know. Indeed we are often bewitched by the theoretical elegance of scientific theories into thinking that we have the key to nature at last. This is especially true with modern science – after all, its great precisions have produced breathtaking technological successes.

It is only after a crisis brought on by the discovery of anomalous information that science gradually enters what the philosopher of science Thomas Kuhn famously called a paradigm shift.³ In the last half-century or so such a shift has indeed occurred in mathematics and in physics, as seemingly complete mathematical descriptions of reality were proven incomplete by the new “limitative” theorems of Gödel, Turing and others.⁴ In their wake has emerged a new mathematics of complexity.

The new mathematics and science thus abandoned the expectation of completeness in mathematical description, and embraced instead a recognition of the unavoidability of incompleteness. It sees formulas as approximations of reality, not as perfect “blueprints.” Moreover, it understands much more clearly the way nature herself uses codes and generative “algorithms” (or sequences of rule-based processes) to produce vastly complex patterns. Such patterns may well be fundamentally unanalysable in any perfect sense.⁵ But they may be, in the memorable phrase of Herbert Simon, “nearly decomposable” into approximate hierarchical schemes. They may lend themselves to modelling and simulation according to analogous or “isomorphic” processes. This is the way that such complex and seemingly “irrational” phenomena as weather patterns and stock markets finally yield themselves to deeper understanding.

In this way we are no longer seeking to “distil” reality down to a perfect blueprint of the mechanics of nature -- for we now understand that such a blueprint does not exist. Rather we are more like “gardeners” of a complex environment. We control it not by mastery of any “fundamental mechanism”, but through intricate and well-developed knowledge of species, growing conditions, rules of hybridisation. We deduce the salient features of the deeper structure of things, as genetics pioneer Gregor Mendel did with his peas, through patient observation, modelling, experiment, induction.

Lest the gardening analogy seem too primitive, make no mistake: these are phenomenally powerful new scientific tools. The new mathematics -- and its algorithmic cousins -- have unlocked many of the secrets of biology and other complex processes. Stock markets, weather patterns, even the most intricate morphogenetic processes of life itself are finally yielding to human comprehension. Without doubt, this is a great historic achievement in human history.

Moreover, we understand now that the structures of the universe are not simply additive assemblies of smaller structures, in a grand rational hierarchy. They are rather structures that are interactive in their totality: they exhibit fields of mutual influence and adaptation, influencing one another as they differentiate in vastly complex ways. We see that when we isolate some part of the structure, we are abstracting it from its real field of influence, and pretending that the field does not matter. This is a trick, of course -- one that is very useful up to a point, but in important ways, an inaccurate reflection of reality. Connectedness, as the mathematician and philosopher Alfred North Whitehead said, is of the essence of all things.

This trick is at the heart of modern science over the last half-millennium. It is extremely powerful, but equally extremely limited. And in its limitations lie its dangers.

The end of the current modernity is the encounter with the dangerous limitations of the usefulness of this trick.

Like science, human culture as a whole has generally developed an increasingly refined understanding of the structure of things. But human culture is lagging behind. The gifts of our age have largely been the fruits of analysis and reduction – counting, sorting, dividing into constituents and re-assembling into a prodigious economic machine. The historic achievements of our times are certainly breathtaking, and should not be underestimated -- sanitation, medicines, agriculture, communication, travel.

And yet, we have paid a price for this reductionism, this mechanical view of the world. We have learnt to pull apart the structures of nature and re-assemble them in myriad ways. But we do not always get them to go back together right – like the mechanic who discovers a few extra parts after the car has gone back together. Perhaps, we hope, the car will run OK. We have discovered an immense power, but we poorly understand what our actions have released. We are like the Sorcerer’s Apprentice, unwittingly unleashing destruction and disorder in our lives and in our environment. The accelerating pattern suggests that we cannot go on like this; it is an unsustainable enterprise.

And yet going on like this is precisely what we are doing. We are trying to cobble onto the old technological architecture a few new gadgets to solve the current set of problems – and we are appalled to discover a new set of problems, thanks to the principle of unintended consequences. That is because we are focussing on the parts, but we are not able to manage the whole. We cannot solve the problem at the level at which it was created.

We are in paradigm crisis.

The new science offers us a path out. It implies tools for a new kind of human technology -- with strong echoes of ancient human patterns – helping us to become more able to adapt to real human needs, more able to comprehend the results of our actions, and hence more able to wield greater responsibility. But we will have to take some of our attention away from the reductive processes, and toward the inductive and the synthetic. We will have to supplement the emphasis on combinations with an equal emphasis on differentiation and adaptation. We will have to embrace the deeper lessons of the new science of complexity.

This implies a transformation of our culture, and of ourselves.

There is another vital aspect of this transformation. The trick of the old science relied upon the notion that nature is a “dead” collection of disconnected “things” without meaning. It was left for other fields like philosophy and religion the question of how meaning and value might get “layered” on to the scheme in some mysterious way. But the picture of nature itself included the core notion that there is no life or meaning to be had in the physical realm.

As science has advanced into the realm of life sciences, this has become an increasing problem. How do we explain the evident teleological qualities of life in a “dead” universe? How do we explain the phenomenon of life at all?

In answering that question science has found itself in uncomfortable territory, having to acknowledge the place of value in a more complete and more accurate scientific would view. As the philosopher Whitehead observed, we belie the existence of value at the moment we form a concept of a bit of matter. It is only “matter” because it “matters” to us – because we can experience it, observe it, feel its impact upon our lives and our structure of meaning as observers. It is an inescapable a priori of science, and a more complete science must acknowledge it in some way.

Simple, brute “facts” do not underlie the formation of human value; rather, human value underlies exceedingly abstract and synthetic “facts.” To reverse this order of concrete and abstract is to commit what Whitehead called “the fallacy of misplaced concreteness.”

In the sciences of life, and in particular the neurosciences, there is emerging today a surprising integration of geometry and human experience – particularly the experience of “meaning”. This integration of meaning cannot be explained away as a “psychological” phenomenon – for who is experiencing this phenomenon, other than the scientist who feels its value and meaning in the first place? How can a scientist who begins with a notion of the value of doing science claim that there is no place in the structure of things for value? That is a rather embarrassing contradiction, after all – an inability to explain matters beyond a certain level of thoroughness.

Thus science is returning however reluctantly to the notion, as the philosopher Whitehead and others have described, that nature is in some primordial sense “alive”. This is a view that finds no opposition between “matter” and “spirit.” The geometric arrangement of matter is simply a manifestation, in varying degrees, of what we experience (in the first place, before any knowledge of “matter”) as transcendent value or “spirit”.

It is the nature of understanding that the meaning and value on which it rests will always remain an impenetrable mystery forever at the heart of things. It is like the knife that cannot cut itself, or the finger that cannot point to itself, as the Buddhists say. Nevertheless, science can articulate astonishing patterns of relationship and structure. They do not “explain away” the mystery, but they deepen and enrich it.

It is important to note that this view of things puts beauty back at the heart of objective reality, as a structural phenomenon. After all, the most beautiful music – a canon of Bach, an Indian raga – is nothing more, or less, than a pattern of vibrations in the air. That is all. And yet for us participating in it, that is everything.

Our reductionist science wants to see this phenomenon as nothing more than “psychological.” But as we have seen, that is an alluring philosophical trick that actually explains nothing – for who or what is perceiving the psychology? We deceive ourselves if we think we can “explain out” our own participation. We cannot; it is always there, always mysterious.

We cannot explain the natural world of beauty and meaning in elemental terms of a “dead” collection of structure. But we can explain the world of structure in terms of beauty and meaning. It is not meaning and value that is an additive trick of structure, but rather structure that is imbued with meaning and value.

Thus do we turn the old mechanist world on its head.

The new science confirms that there is indeed mechanism within the universe. Phenomena do indeed operate in relative autonomy – but within a totality that is not a mere assemblage of fundamentally discrete phenomena, but a web of interaction. We ignore this totality when we abstract specific elements, and pretend that they are fundamentally discrete. But this is a trick – in Whitehead’s words, “nothing less than an omission of part of the truth.” And it is the trick that makes us believe in a “dead” universe of detached elements that can be recombined in endless ways, as we have done so well in our technological age. But in this model we have been unable to explain the phenomenon of life.

The new science is able to explain the phenomenon, or at least point to its origin. The living force is not on an unseen plane, but all around us. It is not in the details but in the totality, and in us as intelligent beings. We cannot “explain” it in terms of something “dead” and “atomic” – but we can articulate specific aspects of its structure with greater and greater approximation to the reality.

All of this taken together implies a profound transformation of science -- and a transformation of our current elementary technological culture. It is time to throw off the crude abstractions of our technological infancy, and step out of the artificial into the rich complex world of nature. Nothing less than our very survival depends upon it.

III. Seven Geometric Properties of Complexity

The new science gives us tools to see what has happened in these earlier stages of modern technological culture. We see that what we mistook for sophistication was in fact a crude and elementary form of machine technology. We see that the obsession with precision has become a pointless fetish. We see that the effort to strip structures down to their “pure” minimalist form was in fact an accommodation to an elementary and primitive technology, dressed up in the guise of sophistication. And we see that our ignorant reductionism has done great violence to the adaptive processes on which nature depends.

This is an enterprise that is unsustainable, in the most fundamental sense.

We can see the failures of the old technological architecture by identifying some of its missing structural qualities. We can see that while we thought we were being sophisticated in our minimalism, we were in fact only manufacturing incompleteness on a profound scale. In so doing we did great violence to the biosphere, and to the subtle but essential qualities of human life. We see, like doctors newly recognising the signs of a disease, that we have created a sickness of place that we could not even recognise in the old model of technological reality. We were bewitched by our own abstractions.

Following are seven of these missing morphological qualities. They exist in abundance in nature, and in human nature. They are ubiquitous in traditional societies, and in the great architecture of history. They are missing from modern architecture and modern culture – not because this is a desirable state of affairs, but because our modern technology has not been sophisticated enough to generate these qualities, or even to understand them. We lack them not because we are sophisticated, but because we are backward and ignorant.

In discussing these properties we must remember that it is not enough to simply add in such qualities through some artificial means, but rather that we must understand the processes that generate such morphology. We will discuss such processes in the next section.

The seven properties are:

¨ Network Structure

¨ Near Decomposability

¨ Fractal Geometry

¨ Adaptive Iteration

¨ Geometric Holism

¨ Structural Attractors

¨ Connective Symmetries

Network Structure

As Christopher Alexander pointed out in his landmark paper of 1964, a city is not a “tree.”⁶ It is in fact a dense network.

To explain what this means in urban terms, let me offer a specific example.

From the book Over Europe, Text by Jan Morris (Weldon Owen Inc., 1988)

On the left is a section of Warsaw constructed in the 1970's. On the right is Rynek Starego Miasta, the square at the heart of old Warsaw. The place on the right is not unlike cities and towns that have been built for many hundreds of years of human history; the place on the left is characteristic of cities all over the world built within the last 50 years.

In comparing these two places, I ask you to forget, for the moment, the semiotic significance or the emotional associations of the two images. Forget about cuteness and nostalgia, symbolism and memory. Look at the two places coldly, analytically, as pure mathematical structures.

The structure on the left is a branching hierarchy -- a mathematical “tree.” Building monads are connected by a branching sequence of linear pathways and entries. Each entry serves as the sole point of connection for dozens or hundreds of dwelling units. Each of these units is connected to its neighbours only by elevators or by linear interior corridors.

The connective relationships, the possible number of pathways between units and to the public realm, are much lower than in the example on the right.

Each building's exterior geometry is similarly stiff and hierarchical -- conforming rigidly to relatively simple concepts of line, grid, plane. The connective relationships are again severely constrained by the simple, fundamental (and quite alien to their context) geometries that are imposed.

The structure on the right exhibits the classic structural characteristics of network. Residences are for the most part directly connected to the plaza space, and hence to each other via innumerable pathways. Buildings are physically connected to each other through an iterative process that produces intense variety with a remarkably limited palette of materials and forms. On many levels of scale, the entire structure is richly connective.

The structure on the right exhibits other connective properties of natural structure that have also been described by mathematical analysis: the iterative generation of complex form using simple rule-based processes and patterns; the fractal repetition of forms and textures at smaller and larger scales; the differentiated adaptation of many elements to a complex biological pattern; the emergence of an overall pattern of coherence and beauty from relatively autonomous elements operating in simple and direct response to their environment.

Note that the structure on the right also has aspects that are strongly hierarchical (the schematic plan of an individual house, the relation of all buildings to the central plaza, etc). The difference is that the structure on the left is rigidly hierarchical, and lacks the network aspects of the structure on the right. The structure on the left is generated by a grand abstraction imposed on the site - the ultimate act of hierarchy. (Readers of Le Corbusier will recognize it as the tower in the park.)

The ignorant conceit of the twentieth century was its belief that the type of structure on the left is actually more sophisticated and "modern" than the type on the right. We now know that the converse is true. Technological prodigy is not to be confused with cultural advancement.

By the way, there is another interesting aspect of the structure on the right, Old Warsaw: it is not really old at all. It was entirely rebuilt in the late 1940's from photos and other historic records after being obliterated by WWII bombing. This is a reminder that structures formed by complex iteration do not have to be old. They do have to employ the structural processes that in this case took many years to develop. But there is no reason in principle why such a structure could not be developed during any given time period.

Or look at the urban plans of the two places below. On the left is a section of the city of Rome; on the right is a typical post-war American suburb. The structure on the right is a simple tree hierarchy, with limited pathways of connectivity; the structure on the left is vastly more complex.

(From A New Theory of Urban Design, by Christopher Alexander et al., Oxford University Press, 1987.)

Notice that the structure on the left exhibits many smaller hierarchies; but that they are plugged into a vast overlapping network structure. The structure on the right almost exclusively conforms to a single hierarchical scheme, with few network properties.

There is a direct correlation between the kinds of experience in the two structures and their network properties: the structure on the left has rich interconnectivity, framing of views, variety of sequential experiences. It is a delight to wander these streets. It is an engagement of the mind with the deeper complexities of the world. The structure on the right, however, may be conceptually pleasing in its simplicity; but it is severely limited, lifeless, lacking complexity. Travelling these streets is, at best, uninteresting. It is a diminution of the richness of experience.

The richest and most satisfying structures of history consistently exhibit a rich network structure.

Near Decomposability (“Chunks”)

In his landmark paper of 1962, The Architecture of Complexity, Herbert Simon described the properties of complex structures and observed that they tend to contain many “nearly decomposable” hierarchical structures within them. They are “nearly decomposable” because they are features that can be discerned or “decomposed” from more complex patterns; they are not pristine hierarchies, but have interactions between the subassemblies that are “weak but not negligible”. As we saw in the example from the Nolli plan of Rome, the overall structure is dense, interconnected, overlapping. But within that structure one can make out many local hierarchies. They are not perfect – there is overlap between hierarchies, and within them – but they are there in abundance.

By contrast, by imposing a grand hierarchical abstractio