The concepts of error and privation in Spinoza's philosophy are situated in a complex situation. On the one hand, Descartes defines error as a privation caused by the abuse of the will to formulate a judgment. On the other hand, Spinoza removes the main conditions for supporting this thesis, but he keeps defining error as a privation of knowledge. This observation is particularly striking since Spinoza reveals himself to his interlocutors as a severe critic of the traditional notion of privation. Why, then, does Ethics apply the term privation to define the form of the error? What authorizes Spinoza to use the term privation, placed in a dimension in which it is no longer necessary to guarantee the will as its main condition? What is Spinoza’s purpose in evoking this term to describe a subject apparently characterized by a great conceptual difference? Based on these questions, this essay develops a discussion about the concepts of error and privation in Spinoza's philosophy. Our goal is to understand the background and the meaning of these concepts and to evaluate their general implications along with themes such as imagination, language, and superstition. In this context, we assume that the use of the expression "dreaming with open eyes" is relevant to the comprehension of the concepts of error and privation in Spinoza's philosophy, especially to describe the condition in which, even in falsity, individuals believe they know the truth.
Key-words: Spinoza; Descartes, error; privation; dream.