A City is Not a Tree

by Christopher W. Alexander

In 1965, the architect and design theorist Christopher Alexander published a landmark theoretical critique of modern urban design, and by extension, modern design in general. His critique was different from others of the day in that it was not based on a social or political argument, but on a structural analysis, rooted in then-emerging insights from the fields of mathematics and cognition. Here, published again on its fiftieth anniversary, is Alexander’s classic text, together with new interpretive commentaries and discussions by leading theorists and practitioners. This volume is destined to become an invaluable resource for a new generation of students and practitioners.

“One of the classic references in the literature of the built environment and associated fields.”
— Resource for Urban Design Information (rudi.net)

“At a time of increasing concern over the adequacy of design methods, A City is not a Tree broke open and reoriented the debate.”
— Charles Jencks and Karl Kropf

Genres: Architecture, Design, Nonfiction, Urbanism, Science, Art

200 pages, Paperback

First published January 1, 1965

About the author

Christopher Wolfgang John Alexander was an Austrian-born British-American architect and design theorist. He was an emeritus professor at the University of California, Berkeley. His theories about the nature of human-centered design have affected fields beyond architecture, including urban design, software, and sociology. Alexander designed and personally built over 100 buildings, both as an architect and a general contractor.

In software, Alexander is regarded as the father of the pattern language movement. The first wiki—the technology behind Wikipedia—led directly from Alexander's work, according to its creator, Ward Cunningham. Alexander's work has also influenced the development of agile software development.

In architecture, Alexander's work is used by a number of different contemporary architectural communities of practice, including the New Urbanist movement, to help people to reclaim control over their own built environment. However, Alexander was controversial among some mainstream architects and critics, in part because his work was often harshly critical of much of contemporary architectural theory and practice.

Reviews

[sam tannehill · Rating 5 out of 5]

I am currently reading through The Nature of Order. The 50th anniversary edition of A City is Not a Tree is a great support to understanding the thoughts about systems and fields of systems leading into Nature of Order as well as the commentary from other authors linking the two books together. There is an amazing movie that everyone should see, Metropolitan, by Whit Stillman. One of the lead characters, Tom, explains to another lead character, Audrey, that one doesn't have to read a book to have an opinion on it, when you can just read the literary criticism to understand the perspective of the author and the critic. This 50th anniversary edition allows for a little bit of this, but not holey. You will not understand Nature of Order by reading this book, but still the commentaries help a great deal.

[Valeriu]

I really enjoyed "A City is Not a Tree," even though I struggled with some parts. There were sections that were just too complex for me, but the main idea of the book really hit home. It's all about how things can seem straightforward, but if you zoom out and look at the bigger picture, you realize they're much more complicated.

This is something I've seen happen in my own job as a software engineer. Just recently, I had a situation in which someone was completely sure about his decision. I understood why he felt that way—his view was very narrow, and in that small frame, he couldn't believe that he was wrong. It’s hard to see your own mistakes when your world is simple and small. This book does a great job of explaining that feeling.

I also loved the interview with the author at the end. It made me think about how fields like architecture have been discussing these patterns and mistakes for a long time. In software, it often just feels like a battle of opinions. Just because software engineering is so young and there's no history to analyze.

I finished the book feeling like I've only scratched the surface and would love to meet an architect to explain it to me in more detail. But even without understanding everything, I'm happy I was able to find so many connections to my own job and experience.

[Sriraam · Rating 5 out of 5]

An exceptional paper that establishes the nature of the design problem as a semi-lattice structure. This is the basis of Christopher Alexander's life work - to find a method to solve the problem of fitting form to context, the nature of which is a semi-lattice structure.

[S. · Rating 4 out of 5]

I'm glad I waited for this edition to read more about Chirstopher Alexander's revolutionary work.
Although my early curriculum included one of his books Notes on the Synthesis of Form or his notable work A Pattern Language: Towns, Buildings, Construction minor focus was on actually deeply studying both manuals. It was more of a read later if you're curious never a methodology adopted for any studio at that time. and that's of course a SHAME!

Basically this edition is special for many reasons but I'll only list two of them:
1- You get to re-read the seminal paper and see what other urban theorists/scholars/practitioners think about it and how it has influenced or been central to their work/projects/research;
2- The contributors are like The Urban Avengers, you'll find Batty, Bettencourt, Jiang, ... etc all of those who are currently at front of understanding and then imagining future cities.

The best part of this book is that is a great starting point for any urban planner interested complexity science applied to cities, not too many equations and a clear focus on the conjunctions between both disciplines, away from a detailed account of equations that are intimidating in that early stage.

[Logan · Rating 4 out of 5]

I have to say it is an intellectual essay with some good information but I think much of his ideas are matter of perspective. His idea of the semilattice being “natural” and superior to the supposed tree-like organization of cities by planners is just simple another way of organization the same information and looking at it a different way. I think there is an ease of organization of the semilattice to the human mind that we understand it’s structure better than a more disorganized state but that’s just simply a perspective or specific way of viewing the same information. He suggest to use the semilattice as a model to show how “units” in the city interact but I found that it creates too much rigidity and doesn’t accurately tell of “real life” scenarios that happen everyday because the semilattice structure alone only represents a screenshot of what/how a city operates. Also, a semilattice flipped upside down looks like a bush so really it’s unnecessary to go through the trouble. I agree that relying on one way of looking at it organizing and planning a city is not ideal but certainly a semilattice is not this ‘almighty problem solving solution’ as the language makes it seem. Especially when the psychological section of the essay describes how it is more difficult to understand/visualize a semilattice than a tree. Overall, the ‘tree’ and semilatrice are two parts to the same coin so to speak, it’s just different perspective of looking at the same information. It is worth the read for those interested in architecture, Urban Design/planning and society.

[Teddy Jorgensen · Rating 5 out of 5]

"When we think in terms of trees we are trading the humanity and richness of the living city for a conceptual simplicity which benefits only designers, planners, administrators and developers. Every time a piece of a city is torn out, and a tree made to replace the semilattice that was there before, the city takes a further step toward dissociation.

In any organized object, extreme compartmentalization and the dissociation of internal elements are the first signs of coming destruction. In a society, dissociation is anarchy. In a Person, dissociation is the mark of schizophrenia
and impending suicide. An ominous example of city-wide dissociation is the separation of retired people from the rest of urban life, caused by the growth of desert cities for the old like Sun City, Arizona. This separation is only possible under the influence of treelike thought.

It not only takes from the young the company of those who have lived long, but worse, it causes the same rift inside each individual life. As you pass into Sun
City, and into old age, your ties with your own past will be unacknowledged, lost and therefore broken. Your youth will no longer be alive in your old age - the two will be dissociated; your own life will be cut in two."

[Peter Nguyen · Rating 3 out of 5]

I think Alexander’s work was certainly more shocking when it was first published, but I took his theory that modern city planning produces artificial cities because of planners’ reduction of complex systems (e.g. the semilattice) to more simple and non-overlapping solutions as a given (e.g. the tree), probably thanks to the Congress for New Urbanism and Strong Towns. This is what separates the artificial city from older, natural cities.

“The playground, asphalted and fenced in, is nothing but a pictorial acknowledgment of that fact that ‘play’ exists as an isolated concept in our minds… Few self-reflecting children will even play in a playground. Play itself, the play children practise, goes on somewhere different every day.”

[Tony Crispin · Rating 5 out of 5]

Pretty good, definitely some more advanced level theory here but I'm glad the original essay got bookified. Only pieces of criticism is that the order of the essays could flow a little better (the recap of Alexander and his work is 7 chapters in when it should really be the first follow-up) and, I'm not sure if this is the fault of the individual contributors or the editor, but there are weirdly a lot of typos. Not anything book-destroying but enough to annoy me. Either way, necessary reading for all the Alexanderheads out there.

[Allison · Rating 4 out of 5]

I read this for my sister's homework, she's a design student.

Honestly, kind of hard to get through because of Alexander's writing style, but it was really informative and made me think about the structure of the cities around me and how communities are formed.

[J · Rating 3 out of 5]

The paper is really good. But the book selection of articles is not _that_ good in my opinion. There are 2 or 3 that really add up to the discussion, the others are merely summaries of Alexander's work in general.

[Sandy Maguire · Rating 3 out of 5]

Good argument that designed cities are designed as trees (like the data structure), but this is ultimately what makes them fail. Short and sweet, though with some fake formalism around semilattices.

[Dave · Rating 4 out of 5]

Gains depth in juxtaposition to Alexander's first attempt at design methods, Notes on the Synthesis of Form. Comes with a mixed bag of commentary.