Scholars know already for a century that  Franciscus Van den Enden was for Spinoza much more than a teacher in Latin and a friend. Plenty of contemporary writings indicate clearly that the atheistic master was the inspirator of Spinoza’s naturalistic philosophy. In 1992 the discovery of the political treatises of Van den Enden opened a new period in the interpretation of Spinozism, especially on the field of political theory. They showed that Radical Enlightenment, only prepared by Descartes’ physics, really started with the revolutionary educational practice, philosophical disputations and political activism of the genius Van den Enden. Spinoza must have been fascinated by the ‘mastermind’; he developed in his treatises (TTP, Ethica, and TP) the theories, which were already severally present in Van den Enden’s works. The international discussion about the precise relation between the famous and decried twin philosophers, which rages in the last decade in the secondary literature, can now for the first time be founded on textual evidence. This book contains the English translation of one of the most original and renewing underground texts in the history of Western civilization.