Spinoza and Descartes on Expression and Ideas

I make the case that Spinoza built on Descartes’s conception of what it means for a mind to have an idea by linking it with his concept of expression because ideas express realities in terms of a causation‑conception conditional (but not vice versa). Briefly, if an idea is caused by a being, then that being is conceived through that idea. Descartes thinks of our clearly and distinctly possessing an idea as a sufficient ground for our expression of what we understand. I take adequate ideas to be their equivalent. Spinoza links the connection and order of ideas with that of things because conceptualization of what is caused and its causes have to coincide (the causation‑conception conditional). Thus, Spinoza’s view must also involve clearly and distinctly possessing an idea as grounds for both expression of its content and the actual existence of a corresponding object of that idea. I stress the intentionality of ideas and discuss what follows from it taken alongside the univocity of being according to Spinoza’s substance monism. Put simply, on both Descartes’s and Spinoza’s views, ideas are always ideas of something. Ideas must express the reality of some corresponding being; in turn, being is itself expressive.