This volume contains Hugo Grotius' first work in the field of Church politics, orginally published in 1613. The book was written to defend the policy of the States of Holland, which was being attacked by the orthodox Calvinistic party in the Netherlands. It was written with an eye to foreign Dutch allies, especially King James I. Grotius' Latin text is here edited critically for the first time and provided with an introduction, an English translation and an extensive commentary. In several appendixes, various texts that are important for the background and the reception of the book are printed, many of them for the first time. Ordinum Pietas is one of the key texts for the knowledge of the religious disputes in the Netherlands during the Twelve Years' Truce (1609-1621).