His reputation as a philosopher was established by his first book, "Philosophy of the Unconscious" (1869; 10th ed. 1890). This success was largely due to the originality of its title, the diversity of its contents (von Hartmann professing to obtain his speculative results by the methods of inductive science, and making plentiful use of concrete illustrations), its fashionable pessimism and the vigour and lucidity of its style. The conception of the Unconscious, by which von Hartmann describes his ultimate metaphysical principle is, fundamentally, not as paradoxical as it sounds, being merely a new and mysterious designation for the Absolute of German metaphysicians.