Perhaps encouraged by his new position as the Pensionary of Rotterdam, a Remonstrant stronghold, Grotius stopped being cautious about his support for the Arminian cause in the summer of 1613. In August that year, he wrote a reply to a pamphlet written by Sibrandus Lubbertus, an orthodox Calvinist theologian at the University of Franeker, in which he had criticized the succession of Arminius at Leiden University. Ordinum Pietas, published in Latin, Dutch (in a translation by Uytenbogaert) and French in October 1613. The first part of the book addresses the succession issue but the second and third parts explicitly defend Arminian principles as well as the government’s autonomy against the Calvinist church. Ordinum Pietas is a furious and unapologetic book, and marks a point of no return. Grotius was now firmly in the Remonstrant camp, and despite a flood of counter-attacks from the Counter-Remonstrants, he would continue to openly advocate religious toleration and reject the interference of the Dutch Reformed Church in state matters.
Hugo de Groot, Ordinum pietas, book, 1613 [1498 C 19]