Spinoza's double dualism
Two types of dualism characterize Spinoza's mature philosophy. The first is the Cartesian dualism of attributes. Although Spinoza's radicalized version of this dualism officially rules out any interaction between matter and mind, his Ethics nevertheless retains a theory of causal precedence between the mental and the physical. In the production of ideas, it is sometimes the mind, sometimes the physical environment that has causal priority. A second, non-Cartesian, type of dualism is to be found in Spinoza's metaphysics of substance. Spinoza's concept of substance resumes the Platonico-Aristotelian idea that agency-causation is limited to what has real being and must be distinguished from the modifications that are its effects. The first, "horizontal", dualism of Cartesian attributes eliminates from Spinoza's psychology any account of behavioral change, and forces him to fall back on the classic idea that we are agents only in so far as we direct our thoughts. The second, "vertical", dualism concerning the ontology of causation, enables Spinoza to introduce a non-arbitrary notion of God, who has a causal role to play that may be distinguished from the workings of the universal clockwork itself. In both cases, rather than expressions of a modern-type naturalism, Spinoza's dualistic positions are motivated by a concern to meet the demands of a Renaissance philosophy of morals, according to which the liberation of the mind and the love of God are crucial elements in the quest for beatitude.