modes of communication." In a later work, Meyrowitz asks: "What are the characteristics of each medium…that make it physically, psychologically, and socially different from other media and from live interaction, regardless of content and grammar choices." Though the term medium theory itself was coined in the 1980s, the roots of this mode of analysis can be found in each major development of a new medium throughout history. In ancient Greece, Socrates observed that writing differed from oral dialogue in several key ways: written texts were incapable of answering questions put to them, reached audiences for which they were not intended, and weakened the memories of those who relied on them. His student Plato continued the tradition, but with a reversal of value judgments about at least some modes of orality versus text: Plato was enthusiastic about writing but wanted to banish the oral poets from his Republic. In the 15th century, Johannes Gutenberg touted the ways in which his own invention of movable type differed in method and potential effects from the work of the scribes. In the 16th century, Martin Luther and his followers consciously exploited the revolutionary potential of print via the first mass-mediated publicity campaign. With the advent of film in the early 20th century, film theorist Rudolf Arnheim defended film as being a potential art form as opposed to a simple mechanical reproduction of reality. He proposed a form of medium theory that suggested that artistic and scientific descriptions of reality were shaped as much by the peculiarities of the chosen medium of representation as by the reality being portrayed. With the growing influence of electronic media in the 1940s and 1950s, political economist Harold Innis offered significant advancements to the development of medium theory with his Empire and Communications (1950) and The Bias of Communication (1951), two books that extend the principles of economic monopolies to the study of information monopolies. Innis rewrote the history of civilization, from early Mesopotamia and Egypt to the British Empire and the Nazis, as the history of communication media and their influences. Perhaps the most notable medium theorist is Marshall McLuhan, who came into the public eye in the 1960s, during the increasing dominance of television, especially with his second medium theory book, Understanding Media (1964). McLuhan suggested that television and other electronic media were having a significant impact on the culture as they diminished the social significance of