  One could interpret the gradual dissociation between Regius and Descartes, and the rejection by the former of the latter’s metaphysics, as an endorsement by Regius of one dominant feature of the Cartesian enterprise, namely, the new natural philosophy that was inaugurated in Le Monde. Regius had followed the logic of Descartes’ natural philosophy by denying any explanatory value in the hypothesis of souls in animals. “Since indeed the actions of beasts … can be explained simply by the disposition of their spirits and other bodily parts, and since entities should not be multiplied without necessity, we have no reason to attribute any intellect to beasts” (Regius 1646, 241–42). He might have followed the same logic in the case of human intelligence, had he not been restrained by his understanding of the teaching of Scripture, and his apparent acceptance on biblical grounds that the human mind is an immaterial substance. Rather than endorse Cartesian metaphysics, as found in the Meditations, which seemed to return its author to the scholastic philosophy that he explicitly rejected, Regius struggled with the competing demands of Scripture and the logic of Cartesian natural philosophy. The challenge of this conjunction is evident in Regius’ repeated attempts to describe the unity of mind and body ‘in a single substance’ (1646, 248) while maintaining that the mind is “something that is really distinct from the body and is separable from it in reality” (1646, 246). This epistemic dualism, to the effect that we acquire some beliefs from natural knowledge and others from Scripture, has been understood, by some readers, as intellectually dishonest and as a typical libertine camouflage for cryptic materialism (Hallyn, 2005). But, as Bos (2013) shows, Regius may have accepted the limits of human knowledge, based on reason and experience, and also adopted a commonplace understanding of the certainty of Scripture. By doing so, he became a reluctant dualist without endorsing Cartesian metaphysics.