The problem of the knowledge of the thinkingsubstance in the Meditations and in the Objectionsand Replies of Rene Descartes

In this article, the hypothesis is developed that Descartes does not clearly articulate theknowledge of the thinking substance in the Meditations on First Philosophy and in Objections and Replies. It is argued that such exposition is necessary for a comprehensive understanding of the status of Cartesian philosophy at the time of writing the Meditations, particularly to grasp Descartes' conception of the knowledge of the thinking substance in the years 1641 and 1642. Asknown, knowledge of the thinking substance is a fundamental element in Descartes' philosophy.Firstly, Descartes' two modes of presenting knowledge of the thinking substance in the Meditations are examined, highlighting the issues each entails. Secondly, drawing from the Objections andReplies: especially the fifth and seventh, criticisms from Pierre Gassendi and Pierre Bourdin regarding the knowledge of the thinking substance are presented. Both Gassendi and Bourdin emphasize that the text of the Meditations does not sufficiently clarify how the thinking substanceis known. They question the possibility of such knowledge, pointing out the ambiguity andobscurity of Cartesian responses. It is concluded that in the Meditations, Descartes confronts aninsurmountable gap between the ontology of substance and its knowledge, which prompts him tofurther develop and clarify his theory in later writings.