The last two decades have witnessed, especially in Germany and France, the rise of a new discipline, the sociology of knowledge (Wissenssoziologie), with a rapidly increasing number of students and a growing literature (even a "selected bibliography” would include several hundred titles). Since most of the investigations in this field have been concerned with the socio-cultural factors influencing the development of beliefs and opinion rather than of positive knowledge, the term. "Wissen” must be interpreted very broadly indeed, as referring to social ideas and thought generally, and not to the physical sciences, except where expressly indicated.