 In his lecture on metaphysics as in his paper “Leib und Seele,” Stumpf’s main target is Mach’s phenomenalism and neutral monism, which amounts to reducing physical objects and subjectivity to functional relations between sensations (or elements) and inevitably leads, according to Stumpf, to idealism and solipsism. Stumpf published in 1919 a very interesting study on Spinoza’s parallelism in which he proposes an original and unorthodox interpretation of Spinoza’s Ethics. He argues that Spinoza’s parallelism, if understood correctly, has nothing to do with the psychophysical parallelism which was dominant at that time since Fechner. According to Stumpf, the heart of Spinoza’s parallelism rests on the distinction between act (or mental state) and the immanent object towards which it is directed. (Stumpf 1919b, p. 19) This act-content parallelism has its source in Aristotle and has been inherited by Brentano and Husserl via many philosophers from Thomas Aquinas to Descartes and Spinoza. Stumpf argues that this interpretation is consistent with Spinoza’s pantheism insofar as the distinction between the act and its immanent content has been transposed to God in Spinoza’s Ethics. For since God’s intellect is considered by Spinoza as the only possible subject, intentional acts and contents are then necessarily two of his numerous modes or attributes. (see R. Martinelli, 2011) Despite his critique of psychophysical parallelism, Stumpf advocates, like Spinoza, a form of pantheism that is consistent with his deterministic and mechanical conception of nature. In Erkenntnislehre, Stumpf recalls that pantheism is a view that he adopted in 1876 in the course of several discussions with Brentano on theism and this was the position that he already advocated in his lectures on metaphysics in Würzburg and later in Halle. Stumpf’s main argument against theism is its inability to satisfactorily resolve the problem of evil in the world. However, as Stumpf pointed out in Erkenntnislehre (1939–1940, p. 681, 798, 17), in his last writings, Brentano seems to adopt a form of pantheism similar to that of Spinoza. (Stumpf, 1939–1940, p. 798)