In 1964 Kuhn left Berkeley to take up the position of M. Taylor Pyne Professor of Philosophy and History of Science at Princeton University. In the following year an important event took place which helped promote Kuhn’s profile further among philosophers. An International Colloquium in the Philosophy of Science was held at Bedford College, London.  One of the key events of the Colloquium was intended to be a debate between Kuhn and Feyerabend, with Feyerabend promoting the critical rationalism that he shared with Popper. As it was, Feyerabend was ill and unable to attend, and the papers delivered focussed on Kuhn’s work. John Watkins took Feyerabend’s place in a session chaired by Popper. The ensuing discussion, to which Popper and also Margaret Masterman and Stephen Toulmin contributed, compared and contrasted the viewpoints of Kuhn and Popper and thereby helped illuminate the significance of Kuhn’s approach. Papers from these discussants along with contributions from Feyerabend and Lakatos, were published several years later, in Criticism and the Growth of Knowledge, edited by Lakatos and Alan Musgrave (1970) (the fourth volume of proceedings from this Colloquium). In the same year the second edition of The Structure of Scientific Revolutions was published, including an important postscript in which Kuhn clarified his notion of paradigm.  This was in part in response to Masterman’s (1970) criticism that Kuhn had used ‘paradigm’ in a wide variety of ways; in addition, Kuhn felt that critics had failed to appreciate the emphasis he placed upon the idea of a paradigm as an exemplar or model of puzzle-solving.  Kuhn also, for the first time, explicitly gave his work an anti-realist element by denying the coherence of the idea that theories could be regarded as more or less close to the truth.