Ludwig Andreas von Feuerbach (1804–1872) criticized German Idealism as a form of theology, or a rationalization of religion. His project was to invert Friedrich Hegel’s (1770–1831) relationship between the individual and the Absolute. Whereas for Hegel, the individual was an effect or expression of the Absolute, for Feuerbach the Absolute was an effect or expression of the individual. Feuerbach’s main works were: Toward a Critique of Hegel’s Philosophy (1839), The Essence of Christianity (1841), Principles of the Philosophy of the Future (1843), and The Essence of Religion (1846). He collaborated with Karl Marx (1818–1883) and was active in the late 1840s revolutionary period, but then retired from public life and died poor.