  In November 1641, however, the Utrecht professor inaugurated another series of disputations in which he transgressed from medicine to philosophy and, by implication, into theology, and thereby provoked a controversy that continued for more than a decade. The most explicit challenge to established Aristotelian teaching occurred when one of Regius’ students, Henricus van Loon, claimed in a disputation (8 December 1641) that the human mind and body are two distinct substances which are joined together in an accidental union [unum per accidens].  This thesis addressed, perhaps inadvertently, one of the most contentious issues in Christian philosophy and theology, viz.  how to understand the unity of human nature, as experienced by each subject, and at the same time defend the traditional Christian beliefs in the immortality of the human soul or mind and the resurrection of the body. The immortality of the soul seemed to presuppose that the mind or soul was capable of existing without the body and, for that reason, that it should be classified as an Aristotelian substance. When Descartes was informed about this disputation (when it was already too late to recommend amendments), he responded that there was hardly anything more likely to offend or antagonize theologians than to say that a human being “is an accidental being” (AT III, 460: Bos 2002, 90–91).