This is a new collection of essays by F.A. Hayek. It is the third volume in The Collected Works of F.A. Hayek and the second volume in order of appearance. Like other volumes in the series the text is published in corrected, revised and annotated form with a long introduction placing the essays in their historical and theoretical context. Of the fifteen chapters in the present work five have never previously been published, two have never before been published in English and most of the remaining chapters are difficult to obtain - only three of them are available in other Hayek collections. Overall the volume presents much newly published work by Hayek on the methodology of economics, its development as a subject, its key thinkers and its important debates.