Many readers, I suspect, will take the title of this article [Women, Fire, and Dangerous Things] as suggesting that women, fire, and dangerous things have something in common—say, that women are fiery and dangerous. Most feminists I’ve mentioned it to have loved the title for that reason, though some have hated it for the same reason. But the chain of inference—from conjunction to categorization to commonality—is the norm. The inference is based on the common idea of what it means to be in the same category: things are categorized together on the basis of what they have in common. The idea that categories are defined by common properties is not only our everyday folk theory of what a category is, it is also the principle technical theory—one that has been with us for more than two thousand years.

The classical view that categories are based on shared properties is not entirely wrong. We often do categorize things on that basis. But that is only a small part of the story. In recent years it has become clear that categorization is far more complex than that. A new theory of categorization, called prototype theory, has emerged. It shows that human categorization is based on principles that extend far beyond those envisioned in the classical theory. One of our goals is to survey the complexities of the way people really categorize. For example, the title of this book was inspired by the Australian aboriginal language Dyirbal, which has a category, balan, that actually includes women, fire, and dangerous things. It also includes birds that are not dangerous, as well as exceptional animals, such as the platypus, bandicoot, and echidna. This is not simply a matter of categorization by common properties.

Categorization is not a matter to be taken lightly. There is nothing more basic than categorization to our thought, perception, action and speech. Every time we see something as a kind of thing, for example, a tree, we are categorizing. Whenever we reason about kinds of things—chairs, nations, illnesses, emotions, any kind of thing at all—we are employing categories. Whenever we intentionally perform any kind of action, say something as mundane as writing with a pencil, hammering with a hammer, or ironing clothes, we are using categories. The particular action we perform on that occasion is a kind of motor activity, that is, it is in a particular category of motor actions. They are never done in exactly the same way, yet despite the differences in particular movements, they are all movements of a kind, and we know how to make movements of that kind. And any time we either produce or understand any utterance of any reasonable length, we are employing dozens if not hundreds of categories: categories of speech sounds, of words, of phrases and clauses, as well as conceptual categories. Without the ability to categorize, we could not function at all, either in the physical world or in our social and intellectual lives.