Avram Noam Chomsky is an American linguist, philosopher, cognitive scientist, logician, political commentator and activist. Sometimes described as the "father of modern linguistics", Chomsky is also a major figure in analytic philosophy. He has spent most of his career at the Massachusetts Institute of Technology, where he is currently Professor Emeritus, and has authored over 100 books. He has been described as a prominent cultural figure, and was voted the "world's top public intellectual" in a 2005 poll. Born to a middle-class Ashkenazi Jewish family in Philadelphia, Chomsky developed an early interest in anarchism from relatives in New York City. He later undertook studies in linguistics at the University of Pennsylvania, where he obtained his BA, MA, and PhD, while from 1951 to 1955 he was appointed to Harvard University's Society of Fellows. In 1955 he began work at MIT, soon becoming a significant figure in the field of linguistics for his publications and lectures on the subject. He is credited as the creator or co-creator of the Chomsky hierarchy, the universal grammar theory, and the Chomsky–Schützenberger theorem. In 1967 he gained public attention for his vocal opposition to U.S. involvement in the Vietnam War, in part through his essay The Responsibility of Intellectuals, and came to be associated with the New Left while being arrested on multiple occasions for his anti-war activism. While expanding his work in linguistics over subsequent decades, he also developed the propaganda model of media criticism with Edward S. Herman. Following his retirement from active teaching, he has continued his vocal public activism, praising the Occupy movement for example.