Classifying things together into groups is something we do all the time, and it isn’t hard to see why. Imagine trying to shop in a supermarket where the food was arranged in random order on the shelves: tomato soup next to the white bread in one aisle, chicken soup in the back next to the 60-watt light bulbs, one brand of cream cheese in front and another in aisle 8 near the cookies. The task of finding what you want would be (a) time-consuming and extremely difficult, if not impossible.

In the case of a supermarket, someone had to (b) design the system of classification. But there is also a ready-made system of classification embodied in our language. The word “dog,” for example, groups together a certain class of animals and distinguishes them from other animals. Such a grouping may seem too (c) abstract to be called a classification, but this is only because you have already mastered the word. As a child learning to speak, you had to work hard to (d) learn the system of classification your parents were trying to teach you. Before you got the hang of it, you probably made mistakes, like calling the cat a dog. If you hadn’t learned to speak, the whole world would seem like the (e) unorganized supermarket; you would be in the position of an infant, for whom every object is new and unfamiliar. In learning the principles of classification, therefore, we’ll be learning about the structure that lies at the core of our language.