 At Alpbach he was also approached by communists, including the Marxist intellectual Walter Hollitscher, who became his teacher and friend. Feyerabend resisted Hollitscher’s political arguments on the basis of his own “youthful elitism” and “an almost instinctive aversion to group thinking” (p. 73). But although Feyerabend later described himself as having been “a raving positivist” at the time, it was Hollitscher, he says, who persuaded him of the cogency of realism about the “external world” (Popper’s important arguments for realism came somewhat later). The considerations Hollitscher deployed were, first, that scientific research was conducted on the assumption of realism, and could not be otherwise conducted, and, second, that realism is fruitful and productive of scientific progress, whereas positivism was simply a commentary on scientific results, barren in itself.