Four letters by Paul Feyerabend to Thomas Kuhn from the 1950s and 60s were found in Kuhn’s
Nachlass at the Institute Archives and Special Collections of MIT. Two of them deal with topics that were at centre stage of the controversy between the two authors that was ignited by Feyerabend’s reading of
Proto-Structure, the draft version of Kuhn’s
The structure of scientific revolutions. These letters are reprinted here. They are probably the continuation of two letters by Paul Feyerabend to Thomas S. Kuhn formerly published in this journal (
Hoyningen-Huene, 1995).