Describes how human thought has been shaped through the centuries by "tools of the mind", from the alphabet to maps, to the printing press, the clock, and the computer. The technologies we use to find, store, and share information can literally reroute our neural pathways. Building on the insights of thinkers from Plato to McLuhan, the author makes a convincing case that every information technology carries an intellectual ethic, a set of assumptions about the nature of knowledge and intelligence.