  Spinoza arrived at this position by way of a decidedly uncartesian account of attributes. While Descartes held that two substances of the same type can share the same principal attribute, Spinoza rejected this. Any two substances, argued Spinoza, must be distinguished either by their attributes (Spinoza dropped the modifier “principal”) or by their modes. But, since modes are themselves both ontologically and causally dependent on the substances of which they are affections, they cannot be the individuating principle for them. Thus, it must be the attributes themselves that individuate substances (and not just types of substances, as Descartes argued). Similarly, while Descartes held that each substance is characterized by one and only one principal attribute, Spinoza invoked the principle of plenitude to show that substance must have infinite attributes. Based on a variation of the ontological argument, he maintained that substance is pure, utterly unlimited being. It must therefore, he argued, possess infinite attributes, in the dual sense of possessing unlimited attributes and of possessing all attributes. Since substance is characterized by infinite attributes, and since no two substances can share a single attribute, there can be only one substance. This radical monism was repugnant to many who, like English philosopher Anne Conway, saw that it eliminated any and all distinction between the creator, God, and His creation.