At the heart of Descartes’s theory of cognition is the act of perceiving an idea. However, it remains unclear what precisely an idea is, what the act of perceiving ideas amounts to, and how that act contributes to the formation of cognition under Descartes’s view. In this paper, I provide an account of perceiving ideas that clarifies Descartes’s notion of an idea and explains the fundamental role that the perceiving of ideas occupies in his theory of cognition. At the end (...) of the paper, I will address an issue that arises regarding the objective reality of ideas and the unity of mind. (shrink)