  Despite the originality of many of Desgabets’s ideas, he was orthodox in his Cartesianism (Watson, 1966; 1987). Desgabets adhered strictly to Descartes’s doctrine of matter as body extended in three dimensions. Physics, as Desgabets conceived it, was both mathematically and metaphysically grounded in the solid of the geometer. He also maintained the substance dualism of mind and matter while retaining their causal interaction. And he, like Descartes, insisted upon the substantial unity of man and the specificity of his nature and defended the Cartesian interpretation of ideas against such non-orthodox Cartesians as Malebranche. Although he claimed that the nature of the mind-body union is “the most impenetrable thing in the world,” he had much to say about its sensory basis and its operations. 