 The second metaphysical topic to which Stumpf attaches great importance in his writings is that of psychophysical relations. Unlike most of his contemporaries, including Brentano and Husserl, Stumpf unequivocally rejects the doctrine of psychophysical parallelism according to which the physical and the psychological are aspects of one and the same reality and advocates, following Lotze, a form of interactionism that rejects monism in favour of dualism. The position that Stumpf defends in “Leib und Seele” and in his two studies on Spinoza, may be summed up by the following excerpt taken from his posthumous book: