society and business are often expressed in Kuhnian terms, however poor their parallel with the practice of science may seem to scientists and historians of science. The terms "paradigm" and "paradigm shift" have become such notorious clichés and buzzwords that they are sometimes viewed as effectively devoid of content. Criticisms The Structure of Scientific Revolutions was soon criticized by Kuhn's colleagues in the history and philosophy of science. In 1965, a special symposium on the book was held at an International Colloquium on the Philosophy of Science that took place at Bedford College, London, and was chaired by Karl Popper. The symposium led to the publication of the symposium's presentations plus other essays, most of them critical, which eventually appeared in an influential volume of essays. Kuhn expressed the opinion that his critics' readings of his book were so inconsistent with his own understanding of it that he was "tempted to posit the existence of two Thomas Kuhns", one the author of his book, the other the individual who had been criticized in the symposium by "Professors Popper, Feyerabend, Lakatos, Toulmin and Watkins. A number of the included essays question the existence of normal science. In his essay, Feyerabend suggests that Kuhn's conception of normal science fits organized crime as well as it does science. Popper expresses distaste with the entire premise of Kuhn's book, writing, "the idea of turning for enlightenment concerning the aims of science, and its possible progress, to sociology or to psychology (or ... to the history of science) is surprising and disappointing." Concept of paradigm Stephen Toulmin defined paradigm as "the set of common beliefs and agreements shared between scientists about how problems should be understood and addressed". In his 1972 work, Human Understanding, he argued that a more realistic picture of science than that presented in The Structure of Scientific Revolutions would admit the fact that revisions in science take place much more frequently, and are much less dramatic than can be explained by the model of revolution/normal science. In Toulmin's view, such revisions occur quite often during periods of what Kuhn would call "normal science". For Kuhn to explain such revisions in terms of the non-paradigmatic puzzle solutions of normal science, he would need to delineate what is perhaps an implausibly sharp distinction between paradigmatic and non-paradigmatic science. Incommensurability of paradigms In a series of texts published in the early 1970s, Carl R.