Phänomenologie des Geistes (1807) is Georg Wilhelm Friedrich Hegel's most important and widely discussed philosophical work. Hegel's first book, it describes the three-stage dialectical life of Spirit. The title can be translated as either The Phenomenology of Spirit or The Phenomenology of Mind, because the German word Geist has both meanings. Phenomenology was the basis of Hegel's later philosophy and marked a significant development in German idealism after Kant. Focusing on topics in metaphysics, epistemology, physics, ethics, history, religion, perception, consciousness, and political philosophy, The Phenomenology is where Hegel develops his concepts of dialectic (including the Master-slave dialectic), absolute idealism, ethical life, and Aufhebung. The book had a profound effect in Western philosophy, and "has been praised and blamed for the development of existentialism, communism, fascism, death of God theology, and historicist nihilism."