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book review

What is an apple like?Raymond Gregory/Getty Images/iStockphoto

My first grade-school reader was titled A Duck is a Duck. No argument there, I thought. Already I had learned a few things about ducks: They have feathers and a beak; they can swim and fly. No doubt I had observed that pigeons are sort of like ducks (they have everything except the swimming part); ostriches, meanwhile, don't look much like ducks or pigeons – they can't even fly – but they're close enough to ducks and pigeons to deserve the label "birds."

Of course, airplanes have wings and can fly – they're not birds, but perhaps we can place them in a larger category of "things that fly." Knowing what makes a duck a bird and what makes a plane not a bird may not seem like very profound mental feats – but Douglas Hofstadter and Emmanuel Sander see such cognitive connections as part of an extraordinarily profound process.

In fact, they see the task of putting things into categories, and the related task of drawing analogies, as the very essence of thought. (It is not giving too much away to reveal that, toward the end of the book, they argue that these two tasks are really the same thing.)

The jacket copy for their hefty new book proclaims it as "an ambitious new theory of how the mind works" – a bold claim, which, if it came from lesser minds, would call for extreme skepticism.

But Douglas Hofstadter, a cognitive scientist and computer scientist at the University of Indiana, is widely regarded as an intellectual heavyweight, and when he says that "analogy-making defines each instant of thought, and is in fact the driving force behind all thought," one feels compelled to at least hear him out.

After all, his first book, Gödel, Escher, Bach (1979) won the Pulitzer Prize, and a string of follow-ups have established him as one of the most creative scientific thinkers of the past few decades, a highly skilled conveyor of complex ideas. His younger co-author, Emmanuel Sander, is a psychologist at the University of Paris.

They begin inside the mind of an infant: A child's first thought, the authors suggest, is "mommy"; the child identifies this concept with a specific physical entity, namely the caregiver who provides food and comfort. Later, she learns that other children also have mommies, and, eventually, that animals have mothers too; and also that "father" is similar to "mother," but not quite the same thing. This impulse to categorize and compare stays with us, for "analogy is our perennial dancing partner."

For scientists, categorization and analogy-making are even more crucial. Consider Galileo's first observations with the newly invented telescope. Before Galileo, there was only one "moon," namely the Earth's moon; to speak of "moons" was simply gibberish. But when the Italian scientist observed four small, star-like bodies seemingly revolving around Jupiter, he was forced to do a rethink: Any celestial body that revolved around a larger one might very well deserve the label "moon."

Another example is the broadening of the category "number" to include quantities less than zero. Today, any fifth-grader can add and subtract negative numbers, but in 16th-century Italy, they were simply unimagined. When negative numbers were finally granted the same status as positive numbers, a whole slew of vexing problems suddenly yielded simple (or at least manageable) answers. The book's most persuasive section involves the physics of the early 20th century, as the authors focus on the thought processes of Albert Einstein, whom they label an "analogizer extraordinaire."

Be prepared to become hyper-conscious of the myriad of analogies one makes every moment of every day. ("He's using this Starbucks as his office"; "City Hall is a circus"; "This book is a bit like a doorstop.") And be prepared for overkill: The question of what is and what is not a "sandwich" goes on for several pages. And a list of what the authors call "caricature analogies" runs through 24 examples, at which point we are told: "Such a list could be extended forever." No kidding.

The dangers of putting things into categories gets only a brief mention. Recognizing that kangaroos and koalas are related means that you know your marsupials; but linking "young black man" and "criminal" simply makes you a racist. And think how much is at stake when a politician or a news outlet classifies a violent attack as "gang-related" or an "isolated incident" or an "act of terrorism." Hofstadter and Sander do not address these questions. They only briefly mention the problem of stereotypes, which "have a bad reputation" but are also "crucial to our survival." They later note that stereotypes "are a frequent source of deeply erroneous categorizations" – a warning that comes three pages from the end of the book.

Some of the arguments in Surfaces and Essences feel a little dated – after all, the power of metaphor is hardly news, and Einstein's thought processes have been probed up, down, and sideways. Meanwhile, some current topics, such as neuroscience, are simply bypassed. The end result is a book that is ambitious and provocative, though unfortunately lacking the originality and spark of Gödel, Escher, Bach.

Dan Falk is a Toronto-based science journalist. His next book will explore the connections between science, art, and literature in the Renaissance.