Spinoza believed God exists and is abstract and impersonal. Spinoza’s system imparted order and unity to the tradition of radical thought, offering powerful weapons for prevailing against “received authority.” As a youth he first subscribed to Descartes’s dualistic belief that body and mind are two separate substances, but later changed his view and asserted that they were not separate, being a single identity. He contended that everything that exists in Nature (i.e., everything in the Universe) is one Reality (substance) and there is only one set of rules governing the whole of the reality which surrounds us and of which we are part. Spinoza viewed God and Nature as two names for the same reality,[69] namely the single substance (meaning “that which stands beneath” rather than “matter”) that is the basis of the universe and of which all lesser “entities” are actually modes or modifications, that all things are determined by Nature to exist and cause effects, and that the complex chain of cause and effect is understood only in part. His identification of God with nature was more fully explained in his posthumously published Ethics. That humans presume themselves to have free will, he argues, is a result of their awareness of appetites while being unable to understand the reasons why they want and act as they do. Spinoza has been described by one writer as an “Epicurean materialist.”
Bento (in Hebrew, Baruch; in Latin, Benedictus) Spinoza is one of the most important philosophers—and certainly the most radical—of the early modern period. His thought combines a commitment to a number of Cartesian metaphysical and epistemological principles with elements from ancient Stoicism and medieval Jewish rationalism into a nonetheless highly original system. His extremely naturalistic views on God, the world, the human being and knowledge serve to ground a moral philosophy centered on the control of the passions leading to virtue and happiness. They also lay the foundations for a strongly democratic political thought and a deep critique of the pretensions of Scripture and sectarian religion. Of all the philosophers of the seventeenth-century, perhaps none have more relevance today than Spinoza.
Stanford Encyclopedia of Philosophy