Grotius’s The Truth of the Christian Religion was first published in Leiden in 1627 in Latin. Written in a plain and direct language for his countrymen, this short work aimed to show those who would encounter pagans, Muslims, and Jews that the Christian religion was the true revealed religion. In addition to “fortifying” the beliefs of his fellow Christians, the treatise intended to convince non-Christians of “the reasonableness of believing and embracing the Christian Religion above any other.”Editor Maria Rosa Antognazza suggests that “Grotius claimed the superiority of Christian doctrine and morality and their perfect conformity with the teaching of the most enlightened reason, and at the same time he advocated tolerance for all positive religions. … Grotius rejected the use of any kind of violence, proclaiming that ‘the weapons appointed for the soldiers of Christ are . . . proper to the Spirit.’… Moreover, in an era of bloody and violent confrontations amongst the different Christian confessions, Grotius raised a forceful appeal ‘to mutual agreement.’ All Christians should remember that they ‘were baptized into the same Name,’ that of Jesus Christ, and that ‘therefore there ought to be no Sects or Divisions amongst them.’ ”Hugo Grotius is one of the most important thinkers in the early-modern period. A great humanistic polymath—lawyer and legal theorist, diplomat and political philosopher, ecumenical activist and theologian—his work was seminal for modern natural law and influenced the moral, political, legal, and theological thought of the Enlightenment, from Hobbes, Pufendorf, and Locke to Rousseau and Kant, as well as America’s Founding leaders. Jean Le Clerc (1657–1736), a Genevan by birth, was a philosophical and theological scholar and, through his editorship of leading journals, a key figure in the republic of letters.Maria Rosa Antognazza is a Lecturer in the Department of Theology and Religious Studies, King’s College London. John Clarke (bap. 1687, d. 1734) was a schoolmaster at Hull, an educational reformer, and a translator.Knud Haakonssen is Professor of Intellectual History and Director of the Centre for Intellectual History at the University of Sussex, England.