Review of Cities Alive: Jane Jacobs, Christopher Alexander, and the Roots of the New Urban Renaissance, a book by Michael Mehaffy.

... something was going on at a deeper level that underlay the dysfunction Jacobs and Alexander fought from the 1960s onward. Cities Alive by Michael Mehaffy examines Jacobs and Alexander together to get at the root philosophical problems that created erroneous thinking in city building in the 20th Century, continuing to the present day.

Downtown Portland in the 1960s—a measure of how far that city has revived from the madness of urban renewal.
Downtown Portland in the 1960s—a measure of how far that city has revived from the madness of urban renewal.

Mehaffy compares and contrasts the ideas of Jacobs and Alexander, tracing the roots of their thinking and the problems they identified back to Plato and Aristotle, through the Enlightenment and Modernism and finally post-modernism.

I've read Death and Life and have a thorough understanding of Jacobs's ideas on cities, but I'm less familiar with her influential work on urban economics. I've read some Alexander, but never explored the depth of ideas described by Mehaffy. My understanding of these polymaths—Jacobs with little advanced formal education and Alexander with graduate degrees from world-class universities in physics, mathematics, and architecture—is greatly enhanced by Cities Alive.

Philosophically, both Jacobs and Alexander are "structuralists," Mehaffy explains. They examined and understood cities through their physical structure and the language we use to describe that structure. Jacobs, for example, applied structural thinking when she asked about “the kind of problem a city is,” the ultimate chapter of Death and Life. To Jacobs, cities were not machines, as modernist planners thought. They were more like organic life forms. 

The machine-view of cities and towns came through a hyper-rationalist approach that rejected historical placemaking wisdom in its entirety. In the early to middle 20th Century the world was going through massive technological changes that often brought miraculous and mind-blowing advances: Penicillin, air travel, mass communications, highways and automobiles, and the hydrogen bomb. Traditional knowledge was out and the technical expert reigned supreme.

In Alexander's influential essay A City is Not a Tree, he explores the structure of cities and the mistaken ideas of modernist planners, who thought of planning in terms of hierarchical branching patterns. Picture the dendritic street patterns of modern cities and suburbs that lead to monotonous similarity in sprawling places. Settlements actually work best as "semi-lattice" structures, he explains. Think of the connected networks of streets in traditional cities and towns, a pattern that leads to more complex social and economic connections.