The ambitions of the All Species Foundation have earned praise from some quarters and skepticism from others. The scope of the effort, some critics say, verges on the preposterous. We aren't even sure, they go on, what the precise definition of "species" is. I'm not going to step into the middle of this debate, beyond observing that the human urge to render phenomena into categories is more powerful than any critique of that urge will ever be. The Book of Genesis begins with a taxonomy of species. Aristotle divided the animal kingdom into vertebrates and invertebrates, and the plant kingdom into herbs, shrubs, and trees. "The construction of categories is a basic human imperative," the biologist Jody Hey writes in Genes, Categories, and Species, a provocative new book that shows how our cognitive wiring often dictates the way we divvy up nature. The human brain has an affinity for patterns even when they're trivial: one day last spring, after a Barry Bonds home run, a television sportscaster noted that this was "the fifth successive year Bonds has homered on April 13." Indeed, the brain is so inclined to discern patterns that it finds them where none exist—producing phrenologists, Spenglerians, conspiracy theorists, and political consultants.
The great animating principle behind most productive human endeavor is the resistance to entropy, the impulse toward order. That virtually anything at all can be perceived in categorical terms underlies everything from Twenty Questions to the Dewey decimal system to sentences that begin with the words "There are two kinds of people ..." The process of filling out a tax return amounts to a strenuous exercise in personal taxonomy ("railroad employee"; "qualifying widow"; "married filing jointly").
I keep a small but representative collection of taxonomic schemata in a folder—a kind of petting zoo. It is broken down, needless to say, into categories. Psychology, for instance, has given us taxonomies of personalities (the Myers-Briggs Type Indicator) and of dreams ("falling or drowning," "naked or dressed"). Scholars have picked apart popular culture, producing humorless taxonomies of jokes ("inferential," "paradoxical") and numbing taxonomies of graffiti ("folk epigraphy," "latrinalia").
In the realm of religion, the taxonomy of demons encompasses fates and furies, deluders and ensnarers, incubi and succubi. A Web-site spreadsheet from the University of Notre Dame displays an intricate theological taxonomy of the passions. Under the rubric dolor ("pain") come the subcategories poenitentia ("sorrow for one's moral sins"), invidia ("sorrow at someone else's good"), and acedia ("sorrow that debilitates by taking away even the desire to escape"). Under the rubric timor ("fear") come erubescentia ("fear of what others will think of you if you act in a given way") and agonia ("fear of an unanticipated evil").