Methodology, Money and the Firm brings together Denis O'Brien's most important essays on issues ranging from methodology to competition policy but is primarily focused on the history of economic thought, an area in which he has made a notable contribution. This two volume set begins with Professor O'Brien's work on methodology and includes essays which take their approaches from the history and philosophy of science as applied to economics, and from the role of theory and data in economics. Industrial problems are addressed in the next section, focusing particularly on competition policy but also covering the question of patents and the neglected contributions of Alfred Marshall in the field of industrial economics. Marshall's achievements are also a theme of the third section which deals with the treatment of the firm by economists. Later sections include discussions of money and trade, the history of English economics from Petty to the end of the classical era, and English and Austrian economics after 1870 with essays on Marshall, Robbins and Hayek. The book also includes a specially written introduction in which Professor O'Brien explains the influences behind his work.