This paper will outline Spinoza's argument in Part 1 of his Ethics of substance. He argues that there is only one substance, which is the same as God, that includes everything in the universe. It will walk through each proposition and explain his proof of it, which relies of his stated definitions. This paper will also explain the difference between Spinoza's belief of substance and that of Leibniz from his Discourse on Metaphysics. It will then argue that Leibniz's account of the number of substances superior.
             Spinoza's first proposition is that "substance is by nature prior to its affections" (Cahn p.417). This proposition relies on his definition of a substance which is self created. The affections of the substance, according to his definition, are things that are created by something else. Since the substance is self-created, the substance must have created the affections from itself. Therefore, the substance is prior to its affections since the substance has to be in existence to create its affections.
             Proposition 2, "two substances having different attributes have nothing in common" (Cahn p.417), also relies on the definition that a substance is self-created. If one attribute of a substance is created from that substance, it belongs only to that substance. Therefore, two different substances having the same attribute are not different, but the same substance. If two substances are truly different, they have none of the same attributes. If all the attributes of the two substances are completely different, they have nothing in common. One thing, which is completely different from the other, cannot have caused the other. This is true because something created must have some knowledge of its creator, as stated in Spinoza's axiom 4. Since the two different things have nothing in common, which includes no knowledge of the other, one cannot have created the other. Spinoza states this in...