The key ideas of Abraham Kuyper's Neo-Calvinism do not come from Calvin or from Reformed sources. Their source is the Christian theosophy of Franz von Baader (1765-1841). Among the many ideas derived from Baader are the ideas of a Christian worldview, a Christian philosophy, the idea of sphere sovereignty, opposition to the autonomy of thought, a Free University, the importance of an embodied spirituality, and the idea of our supratemporal heart, the center of our existence. Seeing these ideas in their historical context of Christian theosophy will challenge many of the current assumptions of evangelicals and reformational philosophers who claim to base their worldview and philosophy on Kuyper's ideas or on the development of these ideas in the Christian philosophy of Herman Dooyeweerd (1894-1977). Part 1 of this book traces the reception of Baader's ideas by Daniël Chantepie de la Saussaye and J.H. Gunning Jr., who then introduced Baader's Christian theosophy ideas to Dutch Reformed theology. Chantepie de la Saussaye and Gunning transmitted these ideas to Kuyper, who acknowledges their influence. Kuyper refers to Baader's writings with approval, and incorporates many of his ideas. Part 2 is a history of the development of Dooyeweerd's Christian philosophy, and of the very different philosophy of his brother-in-law Dirk Vollenhoven. Whereas Dooyeweerd chose to incorporate the ideas of Christian theosophy, Vollenhoven did not. They disagreed with respect to almost every idea in their philosophies. Part 3 is a detailed examination of Dooyeweerd's Christian philosophy. Although Dooyeweerd was not at all forthcoming about his sources, it is clear that there is a deep historical connection of his philosophy to Baader's Christian theosophy, as well as to other mystical and non-Reformed sources. This insight allows us to understand many previously obscure parts of his philosophy and to correct previous misinterpretations of his work. It also opens the way for ecumenical and inter-religious dialogue.