Theodor Undereyck

Theodor Undereyck (born 15 June 1635 in Duisburg, died 1 January 1693 in Bremen) was a Protestant pastor, spiritual writer and pioneer of pietism in the German Reformed Church.

Theodor Undereyck was born in 1635, the son of businessman Gerhard Undereyck and his wife Sara, née Salanger. After the death of his parents in 1636 by the plague, he grew up as an orphan in the house of his uncle Johann Undereyck in Alstaden.

From 1653 to 1658 he studied Protestant theology in Duisburg, Utrecht, and Leiden, under, among others, Gisbert Voetius and Johannes Cocceius. His teachers were partly contrary to one another, but were orthodox Reformed theologians and representatives of continuing reformation. In particular Cocceius strongly influenced him in the direction of a federally theological thought, so that he was also considered one of the major catechists of Coccejanism. Voetius influenced him in the direction of a puritanical way of life and its emphasis on the importance of Christian conventicles. From 1658 to 1659 Undereyck undertook a study trip to Switzerland, France, and England. Bremen 1689; 2. Auflage Bremen 1722; holländische Übersetzung Amsterdam 1702.