In the posthumous "Ethics", "Spinoza wrote the last indisputable Latin masterpiece, and one in which the refined conceptions of medieval philosophy are finally turned against themselves and destroyed entirely." In particular, he opposed René Descartes' famous mind–body dualism, the theory that the body and spirit are separate. Spinoza held the monist view that the two are the same, and monism is a fundamental part of his philosophy. He was described as a "God-intoxicated man," and used the word God to describe the unity of all substance. This view influenced philosophers such as Georg Wilhelm Friedrich Hegel, who said, "You are either a Spinozist or not a philosopher at all."