"At a time of increasing concern over the adequacy of design methods, "A City is not a Tree" broke open and reoriented the debate. It also represented a fundamental change in Christopher Alexander's thinking. While retaining the mathematical foundation underlying his Notes on the Synthesis of Form, "A City is not a Tree" takes it in a very different direction. Where the one seeks a crystalline logic to arrive at the notion of "fitness" between form and programme, the other points to a fundamental ambiguity and overlap in the relation of form to its uses. The one is an extreme extension of Modernist rationalism, the other a reaction against it." Charles Jencks and Karl Kropf


"The tree of my title is not a green tree with leaves. It is the name of an abstract structure. I shall contrast it with another, more complex abstract structure called a semi-lattice. The city is a semi-lattice, but it is not a tree. In order to relate these abstract structures to the nature of the city, I must first make a simple distinction..." Christopher Alexander (1965)

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