  Whether or not Spinoza rejected the predicability of finite modes, it is clear that he did not regard them as either causally or conceptually independent in the way that is requisite for substance. For Spinoza, substance is “in itself and is conceived through itself”, whereas a mode is “in something else and is conceived through something else”. The “in itself/in something else” aspect of these two definitions captures Descartes’s conception of causal independence, while the “conceived through itself/through something else” aspect refers to Descartes’s conceivability-apart criterion for ontological independence. Descartes, it will be recalled, regarded divine substance as both causally and ontologically independent, but created substances as ontologically, but not causally, independent, since they depend on God’s creative (and conservative) power for their existence. It is in this sense that, for Descartes, the term “substance” is used equivocally for God and created substances. Spinoza, however, denied that “substance” is an equivocal term. In so doing, he eliminated two asymmetries in Descartes’s metaphysics—that between divine and created substance, and the asymmetry between extended and thinking substance that Descartes expresses in the Synopsis to the Meditations. For Spinoza, finite minds are not themselves substances, but rather modes of thinking substance. That is, for Spinoza, at the most fundamental level, all minds reduce to the thinking substance of which they are affections.