Johann Heinrich Heidegger was born to Johann Hartmann, dean of the chapter, and Magdalena Wagner, a pastor’s daughter, on July 1, 1633, at Bäretswil in the Canton of Zürich. Johann Heinrich began his theological studies at the Collegium Carolinum in Zürich, and proceeded to Marburg, where he lived with, and studied under, the celebrated Ludwig Crocius, one of the most prominent theologians of the German Reformed Church. He finished his studies at the Heidelberg University, obtaining his doctorate in Theology (1659).
Even while he was wrapping up his studies, his teaching career was beginning. At Heidelberg, he became the assistant of Johann Heinrich Hottinger, the renowned Swiss Orientalist, and received his first teaching appointment at Professor Extraordinarius of Hebrew, and later of Philosophy. Heidegger was translated to Steinfurt (Westphalia), where he filled the chair of Theology and Ecclesiastical History (1659-1665).
While stationed at Steinfurt, two important events transpired in Heidegger’s life. In 1661, he married Elisabeth von Duno, daughter of a Swiss businessman, shaping his domestic life: And, shortly thereafter, he took a study trip into Holland, where he made the acquaintance of Johannes Cocceius, and fell under the influence of his federal/covenant theology, leading to a reshaping of his theological thought.
In 1665, Heidegger was elected Professor of Moral Philosophy at Zurich, and two year later he succeeded Hottinger, his former mentor, in the Chair of Theology. He had truly come home: Heidegger would continue in this post until his death in 1698, declining numerous offers from other prestigious institutions.
While at Zurich, Heidegger rose to become one of the most prominent Reformed Theologians of Switzerland (together with Francis Turretin), and of his age, the period of High Reformed Orthodoxy. Although a man of international reputation and influence, Heidegger was first and foremost an educator. His Corpus Theologiæ Christianæ, and its two abridgements, were leading theological textbooks among the Reformed for half a century. He also produced instructional works on Biblical interpretation and church history. As part of the academic exercises in which he was constantly involved, he published an almost endless series of dissertations, disputations, and diatribes. The Heideggerian corpus is massive, and a monument to his indefatigable industry.
As an educator of theological students, Heidegger had occasion to speak to the controversies of the time. In speaking to the issues that were dividing those professing Christ, he certainly sought truth and precise accuracy of statement, but at the same time, as one longing for unity, he was ever gentle and moderate in his tone. In this way, Heidegger is a model of Christian irenicism. Nevertheless, he shows himself to be a capable polemicist in his writings against Roman Catholic theology and practice.
These qualities are illustrated in his involvement in the composition of the Formula Consensus Helvitica (1675). For more than a generation, the Reformed churches, especially those of France and Switzerland, had been agitated by the aberrant theology arising from the faculty of the Academy of Saumur, and spreading through the churches. Moise Amyraut (1596-1664) was teaching a hypothetical universalism, a modified form of Calvinism, in which God first decreed the salvation of humanity by Christ’s atonement, but, because fallen man cannot believe, a second decree was issued to bless certain individuals with the presence and power of the Holy Spirit, enabling belief. Josue de la Place (1596-1665), denying the immediate imputation of the guilt of Adam’s sin to his posterity, was asserting that man’s guilt was based solely upon his own sin. Adam’s sin does negatively affect his posterity, but not immediately through the imputation of guilt, but rather mediately through the conveyance of a corrupt nature, which sinful and corrupt nature incurs guilt. Finally, Louis Cappel (1585-1658) denied the authenticity and authority of the Hebrew vowel points and accents, introducing a destructive criticism into Reformed theological thought.
In an effort to address these errors, and restore unity to the Reformed churches, it was proposed that a creed be drafted. Heidegger was selected to compose the draft of what would be the Formula Consensus Helvetica. Heidegger’s draft did indeed refute the three principal errors coming out of Saumur, asserting an efficacious redemption, particular and limited atonement, and the inspiration of the vocalization of the Hebrew text; but the entire production was tempered in multiple ways by Heidegger’s moderation. First of all, some of the Swiss theologians desired that the creed contain condemnations of the problematic elements of the Cocceian theology and of Cartesian philosophy; Heidegger passes by these in silence. Second, the tone of the document is moderate and restrained, so much so, that the condemnations of Saumur were actually made sharper before the creed was approved. Third, Heidegger addresses the theological issues, but he does not condemn anyone by name. In Heidegger, rigorous and precise Reformed Orthodoxy is found in a mild and gentle tone.
Although the intention in drafting the Formula was to bring unity to the Swiss Reformed Churches, it had the opposite effect, disquieting the churches and becoming itself an object of debate. The influence and official recognition of the Formula did not last long.
Johann Heinrich Heidegger went to his rest and reward in 1698. A story is told of Heidegger, that he, on his death bed, as he listened to the prayers of his friends, said, “Such prayers are real chariots of Elijah on which to ascend to heaven.”
 Ludwig Crocius (1586-c. 1653) was a German Reformed Pastor and Theologian. He served as Professor of Theology at Bremen from 1610 to 1655, and was chosen as one of Bremen’s delegates to the Synod of Dort. Although caught up in the heated controversies of the age, Crocius is remembered for his gentleness and moderation.
 Johann Heinrich Hottinger (1620-1667) was a Swiss Reformed theologian and philologist. He served as Professor of Church History, Oriental Languages, and Rhetoric at Zurich (1642-1655), and later as Rector of the same (1661-1667), with a brief stay in Heidelberg as Professor of Oriental Languages (1655-1661).
 Johannes Cocceius (1603-1689) was born in Bremen, Germany, and went on to become Professor of Philology at the Gymnasium in Bremen (1630), held the chair of Hebrew (1630) and Theology (1643) at Franker, and was made Professor of Theology at Leiden (1650). He was the founder of the Cocceian school of covenant theology, bitter rival to the Voetian school.
 Francis Turretin (1623-1687) was a Genevan Reformed theologian of Italian descent. After studying at Geneva, Leiden, Utrecht, Paris, Saumur, and Montauban, he was appointed as the pastor of the Italian refugee congregation in Geneva (1648), and later Professor of Theology at the Genevan academy (1653). His Institutio Theologiæ Elencticæ has been heavily influential in Reformed circles, shaping Charles Hodge’s Systematic Theology and Herman Bavinck’s Gereformeerde dogmatiek.