  The intensity of the dispute between Voetius and those whom he identified as proponents of a ‘new philosophy’ might suggest agreement, at least between Descartes and Regius, on a common philosophical position. In the course of the Utrecht controversy, however, an irretrievable breakdown developed in relations between Descartes and his former supporter. The epistemology favoured by Regius, which reflected his disciplinary expertise in medicine and physiology, left little room for Cartesian metaphysics. When he wrote to Descartes, in July 1645 (AT IV, 254–6: Bos 2002, 189–90), that many reputable people believed that Descartes secretly held views about the human mind and God that differed from those that he published, and that he had discredited his philosophy by publishing the Meditations, it seemed to Descartes that Regius was endorsing the same criticisms that Voetius and Schoock had made earlier. The following year, against Descartes’ advice, Regius published the Fundamenta physices, in which he rejected a number of Descartes’ metaphysical theses and thereby incurred the wrath of his former mentor. The French philosopher denounced Regius, as misrepresenting his philosophy, in the preface to the French edition of the Principles of Philosophy (1647). Regius planned to reply by adding twenty-one Corollaries to a medical disputation that was scheduled for 2 October 1647, concerning a forty-year old man who had inflammation of the feet and legs (Regius 1647b). These Corollaries included three of the more contentious claims about the mind and God that Regius had earlier removed from Fundamenta physices in an unsuccessful attempt to appease Descartes. Although the disputation was banned by the University rector, Regius had already disseminated copies of the text, including the controversial Corollaria. Descartes replied with Notae in programma quoddam (1648)—i.e., Notes on a Certain Manifesto—to which Regius replied with an extended version of the Corollaria, in A Brief Explanation of the Human Mind or the Rational Soul, in which is explained what it is and what it may be (Regius 1648).