Individual Certainty and Common Truth: Leibniz’s Philosophical Grounds for Toleration

A noteworthy aspect of the theological controversies arisen both in Catholic and in Protestant fields after the Reformation is the use of Cartesian philosophy for supporting the respective creeds. Theologians such as Antoine Arnauld or Pierre Jurieu appeal to Descartes's theory of judgement, which states that errors depend on the free will, and extend it to every religious or theological error. Hence, according to them, to make a religious or a theological mistake is a voluntary fault, and must not be tolerated. Also for this, a "champion" of toleration like Pierre Bayle harshly criticizes Cartesian epistemology, by denying that errors depend on the will and that the truth is knowable by us. Therefore, Bayle - but also Voltaire, who receives his legacy - give up on the philosophical foundation of toleration and commit it to the State. In this way, toleration becomes more a political practice than a philosophical principle, an idea that, with the present crisis of the States, seems to give rise to many problems. But in the same years another philosopher was developing arguments for religious tolerance without renouncing a strong definition of reason and truth: Gottfried Leibniz. In this paper, we will try to explain, first, Leibniz's criticism to Descartes theory of knowledge and the role it plays in the defense of toleration, and, second, how Leibniz's definitions of truth and knowledge can provide useful arguments for a positive foundation of toleration.