Opera Theologica Quibus orthodoxae Religionis capita perspicuè & breviter explicantur, haeres horum temporum solidè confutantur, ac aliae plurimae utilissimae materiae, eruditissimè pertractantur: Partim antehac non edita, partin ex Germanicâ in Latinam linguam modò conversa, partim emendatiùs recusa, & illustrata: Tribvta In Tomos Tres, Quorum Indicem à Praefatione pagina proxima exhibet: Edita stvdio et opera Quirini Reuteri. S. Th. D. et Professoris in Academia Heidelbergensi. Praemissa vita Autoris, subjecti quintuplices Indices.

3 volumes in 1 binding, (12) 3 462 (924 columns) (32), (8) 882 (1764 columns) (13), (4) 409 (818 columns) (11), 99 p. Later bound in linen binding, Folio.

A complete set of the collected theological works of Zacharias Ursinus (1534–1583), the primary author of the Heidelberg Catechism and a foundational figure in early Reformed theology. A comprehensive and scholarly compilation of Reformation and post-Reformation theological thought, edited and introduced by the Heidelberg professor Quirinus Reuter.

This rare three-volume, bound in one folio binding, titled Opera Theologica, presents an extensive array of orthodox theological treatises, systematically expounding the principal tenets of Christian faith, refuting the prominent heresies of the period, and offering rich academic insight into numerous theological and philosophical matters. The collection includes: 1. Orthodox Reformed theology and dogmatics. 2. Commentary on the Heidelberg Catechism. 3. Refutations of Anabaptist, Roman Catholic, and Lutheran positions. 4. Polemical, pastoral, and exegetical treatises. 5. Catechetical instruction and educational works. The preface contains a biographical life of the author, and the volumes are organized with five separate indices covering themes, Scripture references, doctrinal subjects, and sources. Zacharias Ursinus, 1534-1583, was one of the leading theologians of the Reformation and the principal author of the Heidelberg Catechism (1563), Ursinus played a central role in shaping Reformed doctrine in the German-speaking world. A student of Philip Melanchthon in Wittenberg, he later became professor of theology at Heidelberg, where he authored numerous theological treatises and catechetical works. Ursinus’s writings reflect a clear, Christ-centered approach to Reformed theology, focusing on justification by faith, covenantal structure, and practical Christian living. His commentary on the Heidelberg Catechism became a foundational text for Reformed instruction. The present work, Opera Theologica, compiles his major writings, many of which were previously unpublished or translated from German into Latin. It remains a key source for understanding early Reformed orthodoxy and confessional development in the 16th century.

Some wear is consistent with age, and the text is wide-margined throughout. A small section is missing from the bottom right of the title page, with no loss of text. Browned throughout the book (as usual). No institutional markings. Literature: Schaff, Creeds of Christendom, vol. 3 (on Heidelberg Catechism). / Bierma, An Introduction to the Heidelberg Catechism (2005). / Van der Linde, Catalogus van theologische werken uit de 16e–18e eeuw. / Zacharias Ursinus: The Commentary of Dr. Zacharias Ursinus on the Heidelberg Catechism (Translated by G.W. Williard, 1852).