Abstract Spinoza’s definition of attributes as “what the intellect perceives of a substance, as constituting its essence” ( Ethics 1D4) has led many scholars to endorse an attribute-neutral reading of his metaphysics. According to this reading, attributes like thought and extension pertain to the way substance is perceived, rather than how it is in itself. Yet Spinoza defines God as “a substance consisting of an infinity of attributes” ( Ethics 1D6). No attribute-neutral interpreter has yet explained how an attribute-neutral substance could be defined by its quantity of attributes. To resolve this problem, I propose a new reading of Spinoza’s definition of attribute, arguing that we should understand Spinoza’s attributes as model-dependent , on analogy with the model-dependent dimensions of Cartesian geometry. I use the idea of model-dependence to explain how Spinoza can maintain that having infinitely many attributes is a feature of an attribute-neutral substance.