Inaugural lecture: Chair of Philosophy and History of Scientific Concepts at the College de France, 16 January 2001

In his inaugural lecture for the Chair of Philosophy and History of Scientific Concepts at the College de France, given on 16 January 2001, Ian Hacking develops the idea of styles of reasoning (credited to LudNvik Fleck) and considers the ways in which a style of reasoning introduces new ways of finding out the truth and determines the truth conditions appropriate to the domains to which it applies. In this light he examines some aspects of the thought of Pierre Duhem and Friedrich Nietzsche. He discusses some fundamental distinctions between classifications in the social and the natural sciences and argues that classifications of people and their behaviour have 'looping effects': we need, he suggests, a new type of enquiry concerned with the dynamics of classifying people.