This work does not attempt to present the development of philosophy as the realization of a category of the spirit, even less as its supreme category, or as the gradual conquest of rationality; nor does it believe that this development is the more or less independent result of the transformation of society or the manifestation of a structure of being. Rather the conception of the work is the belief that philosophical doctrines are «facts» comparable to other facts, cultural expressions which do not necessarily constitute a unified experience. This means that the history of philosophy is constituted of ramifications and connections which are not lead out according to a predetermined scheme. At times these ramifications are quite obvious; on other occasions, on the other hand, it is necessary to make suppositions, just like in other historiographic investigations. More than as a unified tradition, history of philosophy is here presented as a multitude of various traditions meeting, conflicting and superseding each other. In this way the reader is provided with the critical point of view which allows him to understand the variety of problems which the changeable conditions of the contemporary world pose. The result of the work of over sixty specialists of different orientations, divided into six volumes, from antiquity to contemporary thought. The first two volumes are concerned respectively with ancient thought and medieval thought, the third covers modern philosophy from the Fifteenth to the Seventeenth century, and the following are each devoted to a single century: Eighteenth, Nineteenth and Twentieth. A complete picture of philosophy which takes into account recent research to obtain a simple and systematic whole.