 Baruch Spinoza’s systematic rationalist metaphysics, which he develops in his Ethics (1677) in part in response to problems in the Cartesian system, is also an important basis for Enlightenment thought. Spinoza develops, in contrast to Cartesian dualism, an ontological monism according to which there is only one substance, God or nature, with two attributes, corresponding to mind and body. Spinoza’s denial, on the basis of strict philosophical reasoning, of the existence of a transcendent supreme being, his identification of God with nature, gives strong impetus to the strands of atheism and naturalism that thread through Enlightenment philosophy. Spinoza’s rationalist principles also lead him to assert a strict determinism and to deny any role to final causes or teleology in explanation. (See Israel 2001.)