ofa Theory ofP ractice (1977), and
Technologies of every sort saturate the world of everyday activity: the schoolteacher's books, maps, and ruler; the shopper's list, scales, and pocket calculator; the scientist's test tubes, computer, and table of periodic elements. In a later volume cowritten with Etienne Wenger (1991), Lave discusses the role of technologies and artifacts in everyday activity and particularly in the learning of cultural practices. It is vital to understand the technologies and artifacts used in any human practice-from navigation to shopping to engineering-because the heritage of any given practice is carried in its technologies. Technologies and other artifacts "encode" the knowledge of a community and allow for certain kinds of cultural activity and not others; in this way, then, technologies impact on the individuals who use them. Lave and Wenger use the example of the ali dade used by quartermasters to illustrate that a tool embodies the thoughts, actions, and biases of unknown numbers of users as it has been developed, used, and adapted over the course of the history of the practice of navigation (p. 101). Certainly, writing systems and writing tools provide an analogous case.