The city of Glückstadt (Schleswig-Holstein) was approximately two hundred fifty miles (four hundred km) north of Xanten and located between the Lower Elbe River and North Sea. The city was strategic for the Brandenburg constituency, serving as an international business center and, with Copenhagen, as a Danish royal city.[footnote]Karl Rasmussen, Glückstadt im Wandel der Zeiten (Glückstadt: Augustin, 1966), 2:193.[/footnote] With a significant Dutch (trading) presence cooperating with Portuguese-Dutch Jews, Remonstrants, Contra-Remonstrants, and Mennonites, the city was known for being ecumenical and tolerant, so that the Reformed, Remonstrants, and Mennonites could operate an elementary school together and share a church building.[footnote]Ibid., 2:169–71.[/footnote] The Reformed church of Glückstadt, classis Hamburg,[footnote]Cf. Pontanus, Laudatio Funebris, 10.[/footnote] called Mastricht in 1661 or early 1662 as full-time pastor. The church building had been a gift of the Danish king Christian IV († 1648) and was attended in the summer months by the queen of Denmark, Charlotte Amalie, during Mastricht’s pastorate. In this international and ecumenical environment, Mastricht published, in 1666, the Theologiæ didactico-elenchtico-practicæ prodromus, his first work of theology, and a forerunner of the Theoretico-practica theologia (TPT).[footnote]Petrus van Mastricht, Theologiæ didactico-elenchtico-practicæ prodromus tribus speciminibus (Amsterdam: Johannem van Someren, 1666). Hereafter called Prodromus.[/footnote] The title of the Prodromus indicates, furthermore, a threefold work concerning De Creatione Hominis, De Humilitate et Superbia Erga Deum, and De Conversatione cum Deo—respectively, the creation of man, humility and arrogance with respect to God, and the walk with God—and Mastricht’s first work was listed in the Index Librorum Prohibitorum.[footnote]Petrus van Mastricht, Theoretico-practica theologia: qua, per capita theologica, pars dogmatica, elenchtica et practica, perpetua sumbibasei conjugantur; praecedunt in usum operis, paraleipomena, seu sceleton de optima concionandi methodo (Amsterdam: Henrici et Viduae Theodori Boom, 1682), præfatio, “Sisto tandem theologiæ Theoretico-practicæ, diu promissæ Tomum-primum cujus jam tum a MDCLXV (cum, consilio Celebb. Theologorum Voetii & Hoornbeekii, ejus prodiret Prodromus).”[/footnote] A closer look at the Prodromus reveals that the pastor of Glückstadt begins each chapter with the exegesis of a biblical text in the original language, from which he infers doctrinal, elenctic, and practical considerations—Mastricht’s trademark for all subsequent theological publications. In the fall of that year, Mastricht returned to Cologne when his father passed away—a visit, moreover, that became an extended break from his pastorate and a point of contention between Glückstadt’s pastor and parish. Correspondence of that time shows that the congregation complained about Mastricht’s progressive stand regarding the traditional church order, while Mastricht criticized the congregation concerning his inadequate remuneration and the dilapidated parsonage or manse, reminding them that he was forced to spend the winter of 1664–65 in the Dutch United Provinces. Furthermore, Mastricht asserted, he lacked time for academic work—a desire reflected in his writing of the Prodromus for the “Nazarenes,” the students of divinity. The work is, written upon the advice of Voetius and Hoornbeek,dedicated to his father and to the consistory of the Reformed church at Hamburg[footnote]Members of the consistory included Daniel Sachsio and Andre de la Fontaine as ministers, as well as elders and deacons. Cf. Mastricht, Prodromus, title page.[/footnote]—the latter was instrumental in resolving the strained relationship between Mastricht and the “happy city” (Tychopolis), the Glückstadt congregation. When the prolific writer Simon Oomius (1630–1706), formerly Mastricht’s classmate in Utrecht and minister in Kampen, read the Prodromus, he wanted the author to complete this work of “practical theology.”[footnote]Simon Oomius, Disseratie van de Onderwijsingen in de Practycke der Godgeleerdheid (Bolsward: Samuel van Haringhouk, 1672), 388, “Petrus van Mastricht, die in de jaere 1665 heeft uytgegeven zijn Theologiae Didactico-Elenchtico-Practicae Prodromus, in drie preuven, van de Scheppinge des menschen, van de Ootmoedigheydt en Hoogmoedigheydt nevens Godt, en van de Wandel met God; welcken arbeydt ick van herten wensche volmaekct te sien.”[/footnote] Upon return to Glückstadt, Mastricht received a call by the Royal House of Denmark to serve the church at Copenhagen—a call he declined in favor of a university appointment.