An Additional Route to Ethics Ip5

Abstract Ethics Ip5 is the claim that there cannot be two or more substances of the same attribute or nature. Here I attempt to fill in the demonstration of Ip5 with an unstated Spinozistic premise ( usp ): that what it is to think of a being of a particular attribute or nature is to have an idea of all of the being of that nature and then to focus on a subset of the content of that idea. Spinoza needs Ip5 to apply to substances that have multiple attributes or else Ip5 cannot do the argumentative work that he asks of it later in Ethics . usp enables Ip5 to do that work, and there is reason to think that Spinoza would have expected his readers to see it as obvious.