An accessible reconstruction of Hegel’s attempt to derive all reality from a single concept. In the early decades of the nineteenth century, G. W. F. Hegel came to believe that philosophy was finally in position to achieve something it had striven for since ancient Greece: becoming an objective, demonstrative science. But to achieve this aim, he thought philosophical knowledge needed to be reconceived in a radically new way—as content contained in a single concept just as the oak tree is hidden in the acorn.  In Hegel’s Sole Idea , Mark Alznauer reads Hegel’s mature philosophical system as the unprecedented attempt to comprehend the entire world as the full unfolding of that single concept, which he mysteriously calls “the absolute idea.”  Ever since Hegel set out this program in his Encyclopedia of the Philosophical Sciences in Outline , Hegel’s system has been regarded as the last best hope of philosophy as an autonomous, fully rational science. But while Hegel’s followers regarded the Encyclopedia as the successful realization of the traditional aims of philosophy, his most influential successors thought it instead showed the exhaustion and collapse of that project. Hegel’s Sole Idea  offers a comprehensive interpretation of Hegelian philosophy that allows a fair confrontation with its most provocative and ambitious claims.