July 2009

Becky Ferreira


Complexity: A Guided Tour by Melanie Mitchell

You have to be a nerd to enjoy Complexity: A Guided Tour by Melanie Mitchell, but if you are a nerd (as I suspect you are) you are likely to enjoy it very much.

Complexity is not an assertion of a specific scientific thesis, separating it from much of popular science reading. The hook is simply Mitchell's attempt to take stock of the vast, interdisciplinary and ever-morphing field of complex systems. This is a challenge; trying to take the pulse of a discipline in such rapid flux seems analogous to the efforts of the field itself, such as trying to pin down a concept as nebulous as how a neuron -- just a little, stringy cell -- can, combined with other neurons, give rise to something as intricate and unpredictable as a human personality.

The book succeeds in buckling down much of the field's ambiguity, along with its role in the scientific community. And refreshingly, while laying out the surprisingly diverse set of fundamental theories that compose the framework for studying complex systems, Mitchell never oversteps the achievements of what her field has actually produced. On the contrary, she is stringent about including criticism of every major theoretical or empirical advance, no matter how much the reader might wish that some of the conclusions presented could be irrefutably true. For example, there is a section about how our "internal physiology and anatomy operate as if they were four-dimensional" in order to trick our metabolisms into being more efficient. There is another about how genetic switches explain why humans -- extraordinarily complicated organisms though we are -- have about 20,000-25,000 protein-coding genes while amoebas are floating around out there with 4-6 million. It's very neat stuff, but much of the research has yet to be done, and Mitchell is always at the ready with the appropriate grain of skeptical salt.

However, you can certainly only take out of Complexity what you put into it. This is true for any book, but the stakes are slightly higher with this one. If you do not understand the example models Mitchell includes, it is difficult to see their relevance to the larger theories that are at the core of the book. Even with an active interest in science and mathematics, many of the example systems she provided require a lot of time and effort to fully click. Approaching the book because you want to know the magic behind milk in coffee swirling into the shape of a galaxy will be unsatisfying -- Mitchell's answers are neither clean, simple nor conclusive, and will inevitably involve some manner of conceptually difficult computer simulation.

In a chapter on Kurt Gödel, Mitchell quotes mathematician and writer Andrew Hodges in his observation that "[Gödel's proof] was upsetting for those who wanted to find in mathematics something that was perfect and unassailable." Complex systems are no different; nothing comes together in a neat little package. If anything (and perhaps predictably), complexity seems messier and more ridden with exceptions than any other scientific field. Mitchell's tome on the subject should thus not be read so much for the answers the field has provided as the questions it has raised.

Still, the trickier example problems are tempered throughout the book by Mitchell's energetic prose. Her love for the subject shines through in every chapter, and becomes infectious early on. There is usually a point every few pages where she steps back and (in a more formal way than this) seems to say, "Isn't this the coolest thing?" Even if you hadn't thought it was that cool at first, you might retrospectively revise your opinion. She affectionately shoehorns her family and friends into her example models, and we often get little anecdotes, such as how Gödel, when preparing to receive American citizenship, became fixated with a logical inconsistency he had found in the U.S. Constitution. Albert Einstein had to dissuade him from talking it over at length with an immigration official during his citizenship interview. We also get the occasional joke. The aforementioned amoeba wins the genome contest "hands down" Mitchell writes; "if only it had hands."

The study of complex systems is bound to have an enormous impact on the way we view both natural and artificial patterns of development, and Complexity is surely the harbinger of many books about the fruits this field will produce in the coming years. At its very least, reading it will provide an opportunity to add such fantastic terms as "cellular automata," "cascading failure," "conceptual slippage" and perhaps most satisfyingly, Entscheidungsproblem, German for "decision problem" to one's vocabulary.


Complexity: A Guided Tour by Melanie Mitchell
Oxford University Press
ISBN: 0195124413
368 Pages


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