Introduction

It is widely acknowledged, even among his critics, that Christopher Alexander has been one of the most influential architectural theorists of the second half of the 20^thCentury (Saunders, 2002b, Rybczynski, 2009, Campbell, 2015).  The author of  Notes on the Synthesis of Form (1964), “A City Is Not a Tree” (1965),  A Pattern Language (1977), and other seminal works, is certainly well-cited by other scholars: at this writing, his book A Pattern Language  holds 11,608 citations on Google Scholar, far exceeding most other works of architecture (scholar.google.com, 2019).  There is also evidence that his ideas have also deeply affected many other architects; according to the Pulitzer prizewinning architecture critic Robert Campbell, Alexander “has had an enormous critical influence on my life and work, and I think that’s true of a whole generation of people” (Campbell, 2015).1

Among scholars of an emerging “science of cities” in particular, Alexander’s work is also readily acknowledged.  For example, about “A City Is Not a Tree,” UCL’s Michael Batty has asserted, “Fifty years on from his path-breaking article, there is now recognition that the kind of complexity and diversity he was alluding to is an essential feature of urban living” (Batty, 2015).  Luis Bettencourt, formerly of the Santa Fe Institute and now the University of Chicago, has similarly argued that “By setting a new course for architecture, Alexander almost single-handedly placed its questions among the great mysteries of the universe and offered its perspectives as new starting points for scientific enquiry. Thus, “A City Is Not a Tree” is the beginning of a unified science of cities and of a dialogue between the city as a natural phenomenon and other complex systems” (Bettencourt, 2015).

Yet Alexander’s early 21^stCentury works, particularly the four-volume magnum opus,  The Nature of Order: An Essay on the Art of Building and the Nature of the Universe, have received far less attention.  Indeed,  The Nature of Order  scores less than 1,000 total citations on Google Scholar (the sum of all citations for its four separate volumes). One problem, according to Michael Batty, writing with his colleague Stephen Marshall, is obvious: “The length – and expense – of the books must surely disadvantage their popularity. The work would pack more punch if the essential messages could be summarized in a much shorter volume” (2012).2

The Nature of Order  also provoked an early and hostile reaction in mainstream architectural publications, no doubt attenuating its reception. For example, an early and influential book review in  Architectural Record by William Saunders, then editor of  Harvard Design Magazine , savaged the work as “a self-deceptive, sloppy, ill-informed, and numbingly repetitious book full of contradictions, foggy generalities, and extreme and unsupported assertions” (2002a).  Perhaps worse for Saunders, as he later wrote in his own magazine, Alexander’s overall approach today “has little ‘cultural capital,’ particularly in architecture schools in which newness, art, and complexity are valued, and belief in timeless and universal human needs is considered naïve” (2002b, pp. 1-2).  According to this view, it appears, the man is simply irrelevant.  

Of course, it is difficult to reconcile this view with Alexander’s demonstrably high influence as previously discussed.  One possible explanation is that Alexander started his career on a solid academic and scientific footing, but then veered into a fringe realm of solipsism and pseudo-science, spouting sloppy new-agey ideas without scientific rigour.  Indeed, Saunders and others did seem to support that interpretation.

In this review, I aim to show that on the contrary, whatever the defects of  The Nature of Order in length, editing, or other respects, it represents the clear culmination of a remarkably consistent corpus over a long career.   I will present evidence that Alexander’s work is in fact a straight line from his days as a Cambridge (UK) physics student, in which he has dealt with precisely the same topic throughout: the ancient philosophical subject of  mereology, the relation of parts to wholes, and his own search for useful new design tools to effect their genesis and transformation toward more successful results, from a human point of view.  Evidence for his success, I will argue, comes from the useful application of his ideas by many other designers and investigators in fields as disparate as computer science, engineering, organization management, service design, educational curriculum, biology, and a dizzying number of other subjects. Further evidence comes from the parallels to the work of other philosophers on contemporary problems of knowledge, technology and design, and tantalising hints of useful progress on offer for these problems, as I will discuss. 

After summarizing Alexander’s early work leading up to A Pattern Language , I will turn to the distinct contributions of  The Nature of Order, exploring some of the philosophical parallels, and the ancient and contemporary human problems (like those of mereology) for which he proposes solutions.  I will note that, although Alexander himself has been surprised by the philosophically challenging results of his work described in  The Nature of Order, they are in fact closely related to the findings of a number of other philosophers and scientists – a comparison that Alexander himself was never particularly interested in making. Finally I will offer a preliminary assessment of the relevance of Alexander’s later work to an emerging science of cities, developed in part by Batty, Bettencourt and others.

I will also note that Alexander’s long career – spanning from Gropius’ 1950s Harvard to the digital world of Wikipedia that he helped to shape – reveals as much about the modern history of planning and architecture, and the philosophical issues hardly confronted, let alone resolved, as it does about Alexander’s own diverse, often difficult, but (as I argue) useful and relevant corpus.

Early Work: 1950s to 1965

After studies in physics and mathematics at Cambridge (UK), Alexander turned his attention to architecture, getting a Masters and later the first (and to date only) PhD in architecture at Harvard.  He published his thesis soon after as his first book,  Notes on the Synthesis of Form (1964).  The book enjoyed a wide readership beyond architecture, and was said to be required reading for researchers in computer science throughout the 1960s.  It was also said to be influential for a generation of architectural theorists including Lionel March and Horst Rittel.3

Like Herbert Simon’s classic paper from around the same time, “The Architecture of Complexity” (1962),  Notes addressed the problem of design as a question of part-whole relations.  Both sought to map the structure of that relationship, so that it could be better exploited by designers in a cybernetic age. Both found roughly hierarchical structures, which Simon referred to as “nearly decomposable hierarchies.”  For Alexander, that “nearly decomposable” aspect was key: the connections that did not obey the neat hierarchy turned out to be especially important.

As Alexander put the challenge, how does a designer develop a successful configuration out of the set of elements identified in a design program?  At one time in human history, this could be done through a direct,  intuitive, “unself-conscious process” as he termed it. But in the current age, with its myriad variables and technological formalism, this would have to be done through a “self-conscious process.” His concern was to outline the essential features of such a methodology, so as to aid designers in their task.  The challenge was really to recapitulate the exquisite good fit that was readily observable in so many traditional designs – in contrast to too many modern designs, whose failures and inadequacies, he noted, were becoming painfully evident.

Like Simon, Alexander saw that the parts of a design problem tended to relate to the wholes through a hierarchical relationship: parts have sub-parts, and the sub-parts have sub-sub parts, and so on. Simon used the phrase “nearly decomposable hierarchies,” noting that these structures were not perfectly hierarchical, but only “nearly” so. 

For Alexander, even more than for Simon, this was a key insight.  It was these non-hierarchical relationships, these “overlaps” and web-network aspects, that provided crucial characteristics of the structure.  That insight was the central point of his widely discussed paper of the following year, “A City Is Not a Tree” (1965).  The “tree” to which he referred was a mathematical hierarchy, and as Alexander pointed out, it can be a profoundly limiting structural relationship:

Whenever we have a tree structure, it means that within this structure no piece of any unit is ever connected to other units, except through the medium of that unit as a whole. The enormity of this restriction is difficult to grasp. It is a little as though the members of a family were not free to make friends outside the family, except when the family as a whole made a friendship. (Alexander, 1965)

By contrast, what he termed a “semilattice” – essentially a web-network – had overlap, redundancy, ambiguity, and interactive relationships. For a city, this was an essential feature of its dynamism, its complexity and richness:

It must be emphasized, lest the orderly mind shrink in horror from anything that is not clearly articulated and categorized in tree form, that the idea of overlap, ambiguity, multiplicity of aspect and the semilattice are not less orderly than the rigid tree, but more so. They represent a thicker, tougher, more subtle and more complex view of structure. (Ibid.) 

In that sense, Alexander was going beyond Simon in pointing out the crucial structural overlaps of the “nearly decomposable” web-network, and in drawing key lessons for the optimal functioning of designs, including the design of cities.  However, as Alexander noted, contemporary city planners were not yet heeding that crucial message.  The problem was, in large part, in the way they conceived of the design problem – an insight for which he drew more from cognitive psychology than from mathematics4.  The mind, he noted, tends to default to these more easily managed mental categories – and for planners, that meant dealing too much with tree-like plans:

It is for this reason - because the mind's first function is to reduce the ambiguity and overlap in a confusing situation and because, to this end, it is endowed with a basic intolerance for ambiguity - that structures like the city, which do require overlapping sets within them, are nevertheless persistently conceived as trees. (Ibid.)

However, for cities this can be immensely destructive:

…the city is not, cannot and must not be a tree. The city is a receptacle for life. If the receptacle severs the overlap of the strands of life within it, because it is a tree, it will be like a bowl full of razor blades on edge, ready to cut up whatever is entrusted to it. In such a receptacle life will be cut to pieces. (Ibid.)

“A City is Not a Tree” became one of the seminal planning criticisms of that era, joining  Jacobs’  The Death and Life of Great American Cities and other works to shape the thinking of a new generation of reformers.  Among other impacts, it had the result of slowing the development of so-called “new towns” as well as tabula-rasa “urban renewal” projects.

Yet we might well ask whether the deeper lessons of “A City Is Not a Tree” were really learned by planners and architects, then or since.  Certainly we can see many developments around that world today that continue to be segregated into tree-like components, that are sterile creations of their architect-artists, meant to be admired as gigantic sculptures but hardly  lived in , as a transformative act of overlap, ambiguity, and vitality in its self-organization.  Mostly we are supposed to passively admire the static works of the technical priesthood of makers.

Meanwhile, Alexander noticed an intriguing feature of the scheme he called “the diagrams.”  Because of the overlaps, and because of the fact that some elements were connected by “strong forces” and some by “weak forces,” it was possible to identify clusters of elements that were in fact sub-units – if overlapping ones – of the environment. As he described in the preface to the ten-year anniversary edition of  Notes , he came to refer to these units not as diagrams but as “patterns.”

Part of his insight came from his own work in computer programming.  Using a computer process to model the synthesis he was describing, he noticed that amid the unwieldy torrent of data, he saw recurrent patterns containing the same clusters of elements, forming the same partial solutions to a design problem. Perhaps these patterns could be abstracted, he reasoned, and re-combined in useful ways, while still preserving the essential contextual, web-network structures of the patterns.  This was a breakthrough.

Alexander came to recognize that there was an important relationship to language in this scheme. The beauty of the scheme was that the sub-units could be combined, much as the words of a sentence could be combined in a language-like way.  Just as language allows ambiguity and overlap, and the capacity of, say, poetry, so this “pattern language” might also allow a more poetic combination of design elements. 

This was in fact a mereological application, a way of exploiting the power of language structures to combine and to build up greater wholes, applying the same compositional benefits to the built environment, where they were heretofore woefully absent.  We were getting the mathematical deadness of “tree-like” laundry lists before, gussied up in the costumes of architect-artists.  Now we might get the actual poetry of language once again.

A Pattern Language was not meant to serve as an automated system of design – Alexander soon disavowed “design methods”, the field he helped to inspire – but a technological tool to guide designers in a more fluid process, helping to ensure that the sum of individual bits of design formed a more coherent whole. Once again, the question was how parts could be organized through design to form more coherent wholes – not how wholes could be made mechanically out of regimented parts, however alluringly packaged by architects. 

The recognition of the language-like web-network of patterns was a major advancement in Alexander’s thinking, and it prompted another insight.  Perhaps human beings had already been employing something like a “pattern language” in traditional cultures, developing a web-network of extremely well-adapted elements. Indeed, apparently humble vernacular buildings were in fact remarkably complex and well-adapted to their challenges from a human point of view, Alexander knew. Perhaps something like this process was deeply rooted in human actions as they went about building their own environments in the past. Perhaps this language-like structure – this wholeness in relation to parts – was rooted in the nature of things.

Alexander and his colleagues published  A Pattern Language: Towns, Buildings, Construction,  an initial volume of 253 patterns in 1977, together with a companion volume describing  The Timeless Way of Building,  an organic, piecemeal process, engaging the generative power of language.  

The Nature of Order, 1977-2003

The popularity of  A Pattern Language among a wide audience (well beyond architects) was certainly remarkable.  The aforementioned William Saunders noted that it “may be the most-read architectural treatise of all time” (2002a). Many do-it-yourselfers did purchase the book and use it to build their own homes and other structures.  But Alexander was alarmed to see that many of the resulting structures did not have the wholeness he had expected.  He came to feel that he had not dealt with the problem of geometry sufficiently – that a wholeness in the configurations of the built environment is not possible, unless it is a wholeness in the  geometric configuration of the structure in space.  That set Alexander on a 25-year project to explore wholeness in the geometries of space, culminating in the publication of The Nature of Order.

Here I will summarize the most distinctive ideas of The Nature of Order, assessing their philosophical antecedents and progress made in resolving current challenges. I will then briefly assess progress made in other fields with these and related ideas, before returning to the question of potential useful contributions for a science of cities.

Adaptive Morphogenesis

Alexander devotes a great deal of the discussion in  The Nature of Order to the process of creating particular geometric structures in the built environment, applying an evolutionary adaptive process of the sort outlined previously in The Timeless Way of Building.  This account should be familiar to anyone who is acquainted with the literature on complex adaptive systems.  What Alexander does uniquely is to tease out specific insights and applications for architecture, urbanism, and design.   

Moreover, Alexander sees an intimate relationship between the structures of the human environment and the structures of the natural world. By studying natural structures, and the form-generating processes that create them, we can apply specific lessons to our own structure-generating processes – where they have gone wrong, where they may have gone right, and specific tools and strategies we can distill from that process.  In particular, Alexander sees capabilities in natural form-generating processes hat are superior to current human technologies, and that therefore offer helpful lessons for the improvement of human design and construction.

Specific tools and strategies are discussed in the book, along with prototypical tests and results – although as Alexander acknowledges, they all, to varying degrees, are in need of further development. Among them are “generative codes” (for shaping a group output); “mirror of the self” (for making stepwise design evaluations and decisions); “sequences” (which might be thought of as patterns of process); and “procedures” (combinations of diagnostic and prescriptive sequences applied through a step-wise process, much as a doctor would conduct a medical procedure).

More deeply, Alexander sees the structuring of the human environment as an instance of nature itself at work, and as such, a suitable research subject for a deeper experimental understanding of the universe, its structures and processes.  Just as architecture is informed by the sciences, and by the philosophy of science, so too, Alexander thinks, architecture can be a proper research subject to inform the sciences on topics of structure, complexity and mereology.  This is in part why the book is subtitled “An Essay on the Art of Building and the Nature of the Universe.”  

Once again we see Alexander the mereologist, drawing conclusions about the nature of part-whole relations and their operations by human beings.  Once again we see that Alexander is hardly the first in the line to develop this topic. Perhaps the most obvious parallel (and one of the oldest) is to Aristotle and his “hylomorphism,” that is, his theory of matter and form.  For Aristotle, matter at one scale becomes form at a higher scale, in turn becoming matter at the next scale.  Aristotle even uses an analogy from the built environment: clay is matter that becomes the form of bricks, whereas bricks are matter that become the form of a house, and so on.  (And houses are matter that create form in a city, and so on and so on.)

This brings us back of course to Simon’s “nearly decomposable hierarchies” – or Alexander’s “trees” and “semilattices.”  Clearly Alexander has added something to this very old equation, as we can now see: the language-like structures of ambiguity, overlap, and endless generativity, through a particular kind of web-structure with its own web-processes.  We can now begin to employ these insights to create particular forms and geometries, and compare them to those of natural and ancient human structures, with their remarkable capacities and effects, to learn new lessons and perhaps exploit similar benefits.     

Space as a field of “centers”   

The first step in this spatial mereology is to get a handle on the units of space – what Alexander referred to in a previous paper as “the atoms of environmental structure” (1984). For him these units were “centers” – identifiable nodes of relationship in space that have a salient clustering relationship with other nodes.  This is an essentially contextual picture of structure, or more properly what has been termed a “scientific structuralist” perspective.  More particularly it is a “structural realist” perspective (see e.g. Russell, 1927, or , arguing that, while structure is “all there is,” and reality has no mysterious "nature" underlying its observed structure, nonetheless this structure is itself mysterious, synergistic, and to some degree alive.

Perhaps the closest modern philosopher to this point of view is Alfred North Whitehead (1929), whom Alexander cites at several key points in the book. For Whitehead, the universe consists of “actual entities” or “actual occasions” that are bound up in a relational system that is always in process, always emerging from its precursors.  Life itself is emergent from these structures, and to some degree immanent in them. 

Again, what Alexander adds to this picture is a focus on the specific processes of the built environment, and how they might transform regions of space.  Turning to a phenomenological perspective, he catalogues “15 properties” that seem to characterize consistent groupings of “centers” in nature, at least from the point of view of human experience.  We might think of them as 15 “patterns” along the lines of  A Pattern Language , but this time not of specific design configurations, but a broader collection of the most salient classes of geometrical relationships in our environment. Among them are structures that would be familiar to any modern mathematician or geometer:  fractals (“levels of scale”), local symmetries, boundaries, alternating repetition, and so on.

These properties are not given as specific methodological elements of design (“now use this property, now that”) but rather, as conceptual frameworks for honing the designer’s decision-making and attention to the mereological results. The “15 properties” also have their counterparts in transformations that tend to produce the respective properties (and sometimes others) – for example, dividing, grouping, folding, symmetry-breaking and so on. By understanding how these processes lead to new structures, designers can be more attentive to contextual (and therefore often unpredictable) steps that bring them about. 

Structure-preserving transformations

Alexander points out that a good-quality design is almost always in part a transformation of what existed before, rather than a “tabula rasa” creation of wholly new parts. In this respect, the transformation preserves at least a part of the existing structure.  This process is iterative, adaptive and continuous,  as we can see in natural morphogenesis (Alexander provides many illustrative examples) as well as in traditional human design processes, helping to account for their often remarkably exquisite fit.

Here Alexander gets even closer to Whitehead’s “process philosophy” – but again, this time with the designer’s interest in the hands-on details of the stepwise process, especially from a human and social point of view.  A “maker” (designer, builder, artist, etc.) is immersed in a world of process in which the made result is never static, but only more or less permanent.  The goal is to create a “preferred” outcome. This view is very close to Herbert Simon’s famous definition of design as devising “courses of action aimed at changing existing situations into preferred ones” (1969).  The focus is on the courses of action – the processes – and their relationship to the preferred results, as those are understood and achieved.  

Here is where Alexander, like Simon, packs many new and important questions into that elegant definition.  Who is doing the preferring, and on what basis?  If a group, how do they agree – or can they? How do they know what steps will bring about that preferred result?  What happens when it doesn’t? What happens when the preference changes, when the process opens up new possibilities?  And so on.  Unlike Simon, Alexander formulates at least partial answers to these questions, in the form of his mereological scheme – one that describes structures arising as the result of human transformations in seek of human value.

The role of value and the qualitative cannot be removed from the equation, for the simple reason that this is the aim of a “preferred” outcome, by definition.  That is, it is preferred because a living human being prefers it and values it. This is the unavoidable starting point for any account of design as an empirical process, and any attempt to deny value, or to define it in positivist or mechanical terms, is a kind of “mental trick” that only appears to make it go away.  That it may emerge in structure is not to say that it can be reduced to a “psychological” phenomenon, or otherwise disregarded.

“A science of qualities”

In this we see Alexander the qualitative scientist – and we also see where many architects and positivists begin to misunderstand and discount him, levelling the charge of “pathetic fallacy” and even arrogant forms of absolutism and essentialism (as Saunders for one claimed).  They should become more acquainted with the philosophy of science, and the current problems of subjectivity and “inter-subjectivity” that are of necessity being confronted in many fields including neuroscience, artificial intelligence, philosophy of mind, and many others. While Alexander was not careful to map his own ideas within these often mature fields – indeed he did seem unaware at times of the similar work of others – he can hardly be called out for transgressing some well-established boundary into pseudo-science.  On the contrary, he can be seen at the forefront of a lively topic in the sciences and the philosophy of science, along with many other investigators.  Again, his unique contribution is to make the trans-disciplinary connection between the resulting insights and the structure of the human environment, with abundant structural examples and enticing insights.  

One example of such a parallel philosophical account is provided by the biologist Brian Goodwin, a founder of theoretical biology and a founding member of the Santa Fe Institute. Goodwin, who worked briefly with Alexander, wrote and spoke extensively about the need for a “science of qualities” to inform the next stage of scientific progress (Goodwin, 2002). He pointed out that this endeavour is well-established within the history of science and philosophy, notably in the scientific contributions of Goethe and others. Goodwin also discussed parallels between his ideas and those of Alexander in an interview with architectural historian Brian Hanson (Goodwin, 2003).  

Holism

A key feature of Alexander’s account is the recognition of interdependent, system-wide characteristics that occur within every stage, and that we can only understand and account for as an entirety – a phenomenon more commonly described as holism.   This is certainly not a new idea in science:  in quantum physics, for example, it has been a preoccupation almost from the beginning, notably in the writings of Niels Bohr (1939). For Bohr, wholeness was closely related to the notion of phenomena as inseparable subject-object systems, which must be so regarded as an unavoidable next step in the advancement of science. Bohr’s observation has an intriguing parallel with Alexander’s more phenomenological approach to the design problem. Later proponents of this view of wholeness include the quantum physicist David Bohm (2005), ecologists like E.P. Odom and G.W. Barrett (1971), anthropologists like Vincent Descombes (2014), and philosophers like Hubert L. Dreyfus (1980).  

Once again we see the uniqueness of Alexander’s mereological contribution in its application to design. Always at the core is the idea that good design is not a “tree” of elements working in a neatly reducible system, but rather, a contextual “semilattice,” a field of complex wholes within space, amplifying one another to form larger wholes.  One cannot take this world apart and put it back together again mechanically, any more than one can take a cat apart and put it back together, and expect it to meow.  The structure exists – perhaps lives, in a primordial but real sense – as an irreducible whole, full of web-like interrelationships and dependencies. One may be very precise about “diagnosing” (much as a doctor would do) the particular structure and condition of any part. From there one may develop tools to act on parts and wholes so as to achieve the preferred outcome – usually to “heal” them or make them more whole – but one must look carefully at the totality of the whole at every step.  

Panvitalism

Since Alexander starts with the empirical perspective of the investigator, he also finds himself forced to accept the anti-positivist premise that the life and experience of the investigator is a given, as is the life and experience of their fellow human beings, and others in the ecosystems that surrounds them and on which they depend.  From there it is not too big a leap to regard the built environment itself as an extension of living systems, perhaps no less so than beehives or turtle shells.

Alexander takes this idea one radical step further: like Whitehead, he sees life as an immanent force in nature, which is shaped, amplified or suppressed by various forces in the world, including the actions of human beings.  This “living structure” is a real structure in the world, no less than a human body. This is perhaps the hardest idea for more positivist-oriented investigators to accept in Alexander – what we might call “panvitalism”. For some it is too close to what they would consider a “pathetic fallacy” – projecting one’s own subjective experience of life onto inanimate objects.  

Yet Alexander was hardly the first to imagine what Whitehead memorably referred to as “Nature Alive” (1938).  Like Alexander, Whitehead saw, in the reigning positivist and mechanist conceptions of nature, a confusion over the relation of facts and value, and a failure to recognize that facts are actually secondary abstractions, only derived from the experience of valuation in the first place. “Matter matters,” we might say, because the force of a wall pushing against our fingers, or the effect of an electron stimulating a sensor visible to our eyes, informs our brains about the abstraction (created in our brains) of “matter”.  It “matters” to us.

For Alexander, this means that we cannot avoid the engagement of our own feelings about the world around us, as a primary foundation of judgment.  To do so is not a pathetic fallacy, but rather, an engagement of a highly evolved system of detection of those structural characteristics that most enhance our own lives, and the life around us. Nor can we ultimately make a fundamental distinction between the point of living systems and that of non-living ones, but rather, we must treat them as part of a series of larger wholes, proceeding inseparably up to the largest scales. (Indeed this continuum is described in one of the “15 properties,” which he terms “not-separateness.”)

While this view suggests a complex and ambiguous state of affairs regarding “degrees of life,” it is not (as post-modernists and post-structuralists would suggest) arbitrary or self-invented.  It connects in an essential way to our own deeper structural relation to the rest of the world, and the often shared inter-subjective valuations of others.  Especially, it puts aright our connection to the made world of the maker, in relation to the secondary abstractions we make to do so.

Synthesis

Alexander’s scheme, described over four volumes, goes very far in uniting a number of these ideas. For example, we can increase the degrees of life within a structure by increasing the density of its centres. We can achieve this result by transforming such a structure, preserving and extending its wholeness.  (In fact, he later referred to “structure-preserving transformations” as “wholeness-extending transformations.”) We must do this by engaging ourselves as inseparable observers and qualitative judgment-makers, relying on our own deeper connectedness to these larger systems.  We can share these inter-subjective evaluations with others, since we and they share common connections to human experience and quality.  We, and they, can participate in an enriching process of adaptive morphogenesis at many scales of time and space.  We can do all of this with the various methods, tools and strategies that Alexander profiles along the way.

Potential contributions to a “science of cities”

As discussed, Alexander’s ideas have already been successfully appropriated by many other practical researchers in fields as diverse as computer science, organization management, engineering, service design, and other areas with a design focus. Much of this development began with the application of pattern language methodology to computer science, and so-called “pattern languages of programming” or as they are also known, “design patterns.”

Less well known is that Alexander’s deeper philosophical ideas about process, qualitative methods, inter-subjectivity and holism have also been embraced by many in the computer science community.  Ward Cunningham, one of the pioneers of pattern languages of programming, has said he was first and most deeply influenced by The Timeless Way of Building , and only later by A Pattern Language (2019). Cunningham went on to develop wiki (the basis of Wikipedia and other innovations) and was also a co-developer of Agile methodology, which in turn has had a widespread influence in management and other fields (Cunningham and Mehaffy, 2013).  Alexander’s later ideas in  The Nature of Order are also frequently taken up in the annual computer science conference “Pattern Languages of Programming,” more commonly known as “PLoP”, developed by Cunningham and others from “The Hillside Group”5.

Other fascinating applications of Alexander’s later ideas can be found in biology, probably none more so than a 2009 paper by Newman and Bhat proposing a “pattern language” model for the evolution of multi-cellular life. Several years later, co-author Ramray Bhat wrote a paper comparing Alexander’s ideas more directly to complexity in biological processes, in a paper titled “Understanding Complexity Through Pattern Languages in Biological and Man-Made Architectures” (2014). In his paper, Bhat did look specifically at the ideas of  The Nature of Order , including the formulation of “15 properties” for which Bhat found many analogues in biology.

How then might we also apply these apparently fruitful ideas to the emerging sciences of cities?  As Bettencourt suggested, “Alexander has given us “the beginning of a unified science of cities and of a dialogue between the city as a natural phenomenon and other complex systems.”  Here I suggest several potential contributions from the later work.

A contribution to understanding the dynamics of complex adaptive systems in city evolution.

Alexander describes the detailed workings of complex adaptive systems as rule-based algorithmic processes generate the form of cities, or “adaptive morphogenesis” as he outlines it. The individual actors (not only architects, but also many other participants) are “agents” in a kind of massive “cellular automaton,” following relatively simple rules to produce a complex and largely self-organizing result. If we can tease out these rules, we can make interventions to improve the outcome, following Simon’s definition of design as “devising courses of action aimed at changing existing situations into preferred ones.”6

Alexander’s unique contribution to this subject is to propose a number of “courses of action” in considerable detail (project pattern languages, community mockups, generative codes, etc).  We may question whether these actions are practical or even feasible at this stage; but we may also take the example of the earlier computer science developments as suggesting that others may well take forward more practical methods along these lines.  Already a number of “early adopters” have begun using Alexander’s methods in their own architecture firms and other enterprises, with tantalizing if so far limited results.7

A contribution to understanding building process.    

Alexander has helpfully pointed out some of the actions among a variety of agents within city-building that generate form, or conversely, that constrain form, or cause its degradation into undesirable states from a human point of view – what he terms “massive process difficulties”. We may well dispute the finality of his judgments as to undesirable states – particularly in his critique of modern architecture – but it is certainly undeniable that many human beings who are not architects do share his judgments8, summed up memorably by an introductory passage in “A City Is Not a Tree:”

The non-art-loving public at large, instead of being grateful to architects for what they do, regards the onset of modern buildings and modern cities everywhere as an inevitable, rather sad piece of the larger fact that the world is going to the dogs. (Alexander, 1965).

Of course, Alexander does more than wring his hands at this state of affairs.  In that paper, he gives a mathematical account of the structural relationships that he believes have gone awry, namely, the overly segregated hierarchical “tree” structures of modern city planning.  In  The Nature of Order,  he takes this analysis much farther, examining the processes by which these structures are imposed, and the institutional systems by which this happens.  These he summarises under the generic term “System B,” the institutional counterpart to the “self-conscious processes” of  Notes on the Synthesis of Form , whereas “System A” is the institutional counterpart of the unself-conscious processes described therein. What we need, he concludes, is a transformation in the capabilities of this System B, so that it is able to produce the more satisfactory well-adapted form that he began to describe in his very first work.  Again he proposes many specifics, which again may or may not be fully feasible at this stage – but in any case they suggest promising potential for further development.

A contribution to understanding a more proper relationship between art and science in cities.

William Saunders’ earlier-referenced remark about Alexander’s alleged irrelevance spoke volumes about the confused state of art in contemporary city-making.  His comment – that “in architecture schools... newness, art, and complexity are valued, and belief in timeless and universal human needs is considered naïve” (2002b, pp. 1-2) is remarkably at odds with a science of cities that is concerned with the actual structure of form-generation and its systemic outcomes for human beings, well beyond the scale of specialist artist-architects and their efforts to create “newness” for its own sake. Then too, their own individually imagined expressions of apparent “complexity” now seem quite weak and trivial – rather closer to mere “complicatedness” – in relation to the deeper web-network complexity of the kind of multi-agent adaptive morphogenesis that Alexander describes, in natural systems as well as collaborative human works.

One is reminded of Jane Jacobs’ famous critique of the confusion between art and life, which is not good for life, and probably not good for art as well: “the result of such profound confusions between art and life are neither life nor art: they are taxidermy… this is a life-killing (and art-killing) misuse of art” (Jacobs, 1961, p. 373).

To be sure, Alexander describes a place of honour for art within his scheme of adaptive morphogenesis: it is a kind of enrichment of the structure, an expressive illumination of the existing shared meanings of the city and its buildings. It is not an abstract expression that  supplants the life of the city, with a monstrous out-scale neoplastic sculpture. Rather, it is a rich structural expression that supports and enriches city life and quality.  In that sense, Alexander offers a radical counter-critique of the kind of “commodified art” that seems to pass as mere packaging of older-generation industrial “products,” marketed by Saunders and others.  Seen in this light, their efforts to prop up the old art-led industrial regime (of GM, Armour, Rockefeller et al.) seems the more reactionary by far.   

A contribution to understanding aesthetics as a non-trivial indicator of life-supporting order.

 Alexander makes a deep connection between aesthetics and well-being – and in that sense he joins many contemporary investigators who have shown a link, including Ulrich (1984), Kellert and Wilson (1995), and many others9. Alexander goes a step further, and proposes that aesthetic qualities are in fact indicators that allow us to detect structures that will promote our own health and well-being – that is, our own life and its quality.  He is not the first to see a relation to our own evolutionary psychology – see for example Dutton (2005) but he seems to be the first to propose such a detailed structuralist theory of environmental aesthetics.  For him, aesthetic experiences are the ways we recognize the deep life-supporting order – or conversely, life-degrading disorder – of our human environments.  Again, art plays a role as an agent of enrichment and illumination – but it must be a supportive and nurturing role, in service to the life of the city and its inhabitants.  Alexander concludes that we must move very far, in theory and in practice, from where we are today. 

At present, aesthetics is a controversial topic in architecture and urbanism – elevated on the one hand by those who give prizes for the most aesthetically pleasing architecture (but again, to whom?) – and denigrated on the other hand as a matter of varying taste and relativistic social construction. Alexander points the way to a plausible schema in which aesthetics does have a structuralist anchor, and common shared patterns through history, while leaving ample scope for individual variations and novelties. It would be interesting indeed if these insights could be developed to apply to the city as a complex adaptive system, integrating its cognitive and aesthetic aspects.  There are hints in Lynch and his “imageability” (1960) as well as Jacobs’ discussion of “the uses of visual order” (1961, p. 372-391) . However Alexander takes these insights very far indeed with tantalizing insights, reminding us of a remark by E.O. Wilson that “the science of aesthetics awaits its Mendeleev” (1998).  

A contribution to understanding “modernity” as an incomplete stage in the evolution of technology, design, and city-making. 

For Alexander, the current stage of technology can best be described as a series of mistakes on the way to a wiser application of the powers of technology and abstraction.  Just as “A City Is Not a Tree” pointed out the mistakes and consequences of an overly tree-like conception of the city, so  The Nature of Order pointed out the mistakes of an overly mechanical conception of the generation of form. We could now imagine another kind of technology, more life-supporting, more adaptive to broad human feelings and needs, and capable of producing more satisfying results.  This technology could succeed in that task because it could take seriously the human being, and human life – life in an even broader sense –  as the central aim of its processes.  It could do so now, because it has learned the lessons of the new sciences of complexity – a point that Alexander made well in  The Nature of Order :

People used to say that just as the 20th century had been the century of physics, the 21st century would be the century of biology... We would gradually move into a world whose prevailing paradigm was one of complexity, and whose techniques sought the co-adapted harmony of hundreds or thousands of variables. This would, inevitably, involve new technique, new vision, new models of thought, and new models of action. I believe that such a transformation is starting to occur... To be well, we must set our sights on such a future. (Alexander, 2003, p. 568-570)

Conclusion

We see, then, that in spite of Alexander’s heretical reputation within architecture, his idiosyncratic formats and his own disinterest in drawing parallels, the actual work has always been situated deeply within recognizable and often ancient topics of science and philosophy, from his early work on the synthesis of form to his late-career work on “the art of building and the nature of the universe.”  Topics of mereology (part-whole relations), hylomorphism (the transformations of matter), ethics (what is good architecture, and what is good practice), ontology (the nature of reality), and other perennial human concerns, can be seen throughout his work.  Applications to urban science must be understood against this scientific and philosophical backdrop in order to be intelligible. 

At the same time, Alexander’s contribution of practical tools, methods and insights is prodigious, as we have seen, and spans from computer science to organization management to biology, and other fields not ordinarily influenced by developments in architecture. Seen in that light, Alexander’s incomplete contribution to architecture, especially in his later work, seems to suggest an oversight, perhaps out of a combination of factors – but in any case, with the clear implication of enticing opportunities remaining for further development.   

• 1. Other prominent figures who have acknowledged Alexander’s deep influence across remarkably disparate fields include the architect Rem Koolhaas (2008), sociologist Richard Sennett (2015), Agile co-developer and Wiki inventor Ward Cunningham (2019),  The Whole Earth Catalog publisher Stewart Brand (1995), developer of software hits  The Sims and  SimCity  Will Wright (2003), and musicians Brian Eno (2019) and Peter Gabriel (2017).
• 2. It should be noted that several authors have indeed sought to summarize the key material in a shorter volume, including Alexander’s co-editor Nikos Salingaros (2017) and former collaborator Jenny Quillien (2008).
• 3. A review in Industrial Design Magazine termed it “one of the most important contemporary books about the art of design, what it is, and how to go about it.” I am indebted to Ward Cunningham (pioneer of “pattern languages of programming,” and originator of “wiki”) for information about Alexander’s influence in computer science, and to Marcial Echenique, former Head of the Architecture School at the University of Cambridge, for a personal account ot Alexander’s influence among architectural theorists.
• 4. During his Ph.D. studies, Alexander worked closely with the cognitive scientist George A. Miller, author of the seminal paper “The Magical Number Seven, Plus or Minus Two” (1956).  Alexander later told this author that Miller had a profound influence on him.
• 5. The 2018 program is an example, featuring numerous talks on  The Nature of Order and a keynote by David Seamon, a frequent author on Alexander’s later work.  See https://www.hillside.net/plop/2018/index.php?nav=program. In the interest of full disclosure, this author is also a member of the advisory board of The Hillside Group.
• 6. I am certainly not the first to point this out, as our colleague Besim Hakim has written about this aspect of Alexander’s work as well.  See e.g. Hakim, B. S. (2007). Generative processes for revitalizing historic towns or heritage districts.  Urban Design International, 12 (2-3), 87-99.
• 7. See for example the work of Kubala Washatko Architects of Milwaukee, WI., who feature resources from  The Nature of Order on their webpage (www.tkwa.com). This author also uses a number of methodologies developed in  The Nature of Order  in international consulting work.
• 8. The evidence for this state of affairs is abundant in the literature. See for example Brown, G., & Gifford, R. (2001). Architects predict lay evaluations of large contemporary buildings: whose conceptual properties?  Journal of Environmental Psychology, 21 (1), 93-99.
• 9. See for example an early survey of the research literature in this topic, Cold, B. (1998).  Aesthetics, Well-Being and Health Essays Within Architecture and Environmental Aesthetics. Trondheim: Norwegian University of Science and Technology.