on semiotics, writing many essays on these subjects. In 1962 he published Opera aperta (translated into English as "The Open Work"). In it, Eco argued that literary texts are fields of meaning, rather than strings of meaning; and that they are understood as open, internally dynamic and psychologically engaged fields. Literature which limits one's potential understanding to a single, unequivocal line, the closed text, remains the least rewarding, while texts which are the most active between mind, society and life (open texts) are the liveliest and best—although valuation terminology was not his primary focus. Eco came to these positions through study of language and from semiotics, rather than from psychology or historical analysis (as did theorists such as Wolfgang Iser, on the one hand, and Hans Robert Jauss, on the other). In his 1964 book Apocalittici e integrati, Eco continued his exploration of popular culture, analyzing the phenomenon of mass communication from a sociological perspective. Visual communication and semiological guerrilla warfare (1965–1975) From 1965 to 1969, he was Professor of Visual Communications at the University of Florence, where he gave the influential lecture "Towards a Semiological Guerrilla Warfare", which coined the influential term "semiological guerrilla", and influenced the theorization of guerrilla tactics against mainstream mass media culture, such as guerrilla television and culture jamming. Among the expressions used in the essay are "communications guerrilla warfare" and "cultural guerrilla". The essay was later included in Eco's book Faith in Fakes. Eco's approach to semiotics is often referred to as "interpretative semiotics." In his first book length elaboration, his theory appears in La struttura assente (1968; literally: The Absent Structure). In 1969 he left to become Professor of Semiotics at Milan Polytechnic, spending his first year as a visiting professor at New York University. In 1971 he took up a position as associate professor at the University of Bologna and spent 1972 as a visiting professor at Northwestern University. Following the publication of A Theory of Semiotics in 1975, he was promoted to Professor of Semiotics at the University of Bologna. That same year, Eco stepped down from his position as senior non-fiction editor at Bompiani. Name of the Rose and Foucault's Pendulum (1975–1988) From 1977 to 1978 Eco was a visiting professor at Yale University and then at Columbia University. He returned to Yale from 1980 to 1981, and Columbia in 1984. During this time he completed The Role of the