At the center of his work is Fichte's Science of Knowledge, which he revised seven times. The second presentation, the foundation of the entire Science of Knowledge (1794), in which he discusses knowledge of facts from the principles of object experience, has remained the most influential. In object experience, Fichte not only revealed the practical but also the theoretical principles, thereby demonstrating the connection between theoretical and practical reason. His work became the starting point of German idealism due to this achievement. The text of this fourth edition, reprinted since 1956, is based on the "second improved edition" from 1802, Leipzig. Variants from the first edition of 1794 and the 1802 edition, Tübingen, are noted, as well as Fichte's marginal comments. Includes an introduction, indexes, and a list of editions.