Baruch de Spinoza (1632-1677) is one of those early Enlightenment philosophers who can be rediscovered today through critical inquiry. The ideas in his main work, the Ethics, presented in a geometric manner, lead directly from his metaphysical speculation about the nature of God and nature to the pressing ecological questions of our time. Furthermore, Spinoza addressed the compatibility of natural law and state order in smaller writings, such as the Tractatus Theologico-Politicus. Helmut Seidel succeeds in portraying Spinoza not only as a precious antiquity but also as a contemporary thinker of tolerance, which does not float above reality like a beautiful ideal, but is fully aware of the challenges of its realization.