Baruch Spinoza fits well into the group of seventeenth-century philosophers that includes company like René Descartes, Thomas Hobbes, and Wilhelm Leibniz. Like them, he is systematic, laying out his philosophy as if it were a mathematically deduced proof. Spinoza's metaphysics is unique: he said God was the one substance in the universe. For this claim about God he was criticized as a materialist and an atheist. For people said if everything is God, then God is the material universe. Though widely criticized, and even excommunicated for his thinking, he remains one of philosophy's true original thinkers.