The Historical Dictionary of Philosophy, the Historisches Wörterbuch der Philosophie (HWPh), is distinguished by its particular presentation of philosophical terms, ideas and concepts. Rather than providing mere defintions or descriptive and analytical explanantions the HWPh strictly applies the critical method of history of concepts developed by the eminent German scholar and philosopher Joachim Ritter. By means of precise and detailed references it documents the origin, first occurrence, the historical evolution and the changes of meaning of each concept, from Ancient Greek to contemporary philosophy. For the reader this presentation is of unique value: it makes traceable the importance of terms and concepts at certain periods or for a particular philosopher, as well as its changes and development of meaning.