Spinoza’s Treatise is very much a product of its time—especially the immediate context of the Dutch Golden Age, with its heady mix of economic wealth, political liberalism, religious dissent, scientific and technological progress, cosmopolitan culture, and artistic riches. By the same token, Spinoza’s ideas were well ahead of their time; the world of early modern Europe was not ready to dismiss organized religion as nothing but organized superstition and the belief in miracles as grounded in ignorance. In so far as Spinoza’s scandalous treatise provides the foundations for a modern, secular, and tolerant state, it remains, today, one of the most vitally relevant works in the history of philosophy.A Book Forged in Hell is an addition to my earlier studies of Spinoza and his philosophy: the biography I published in 1999, Spinoza: A Life; a book devoted to his excommunication from Judaism, Spinoza’s Heresy (2002); and a study of the Ethics (2006).With this new book, I have completed what has turned out to be a long-term project on Spinoza, one devoted to making his life and the various dimensions of his thought accessible beyond academia to a broader reading public. It is a life and thought well worth studying today.