Preface

From 2007 to 2011, the editors, together with Marco Panza, invited Michael Detlefsen to direct the project Ideals of Proof (Chaire d'excellence senior ANR-07-CEXC-002-01). This project focused on certain ideals, which guided mathematical reasoning throughout its history. A substantial body of publica­tions and lectures has grown out of this project. They can be consulted under http://halshs.archives-ouvertes.fr/IP/fr/. As a continuation of this project, this special issue of Philosophia Scien..