The Cogito is considered the hallmark of Descartes’ intellectual system, with which a great transformation occurred in the history of philosophical thought. The essence of the Cogito lies in the new meaning that Descartes gives to the soul, and this meaning-making occurs through the transition from soul to mind. The Cogito manifests itself in three important works, albeit in different readings: Discourse on Method, Meditations on First Philosophy, and Principles of Philosophy. However, among these three, Descartes only considers Meditations as a “treatise” and also refers to it as his metaphysics. In the present article, we try to examine the place of the Cogito in Descartes’ intellectual system in terms of the transition from the Aristotelian soul to the Cartesian mind, by focusing on the “Second Meditation” of the six meditations in Meditations. It is clear that for this purpose, we must necessarily present preliminary discussions, especially in the Renaissance period and in the seventeenth century, to clarify that Descartes’ thought in this regard is not only an emphasis on negating the ideas of predecessors, including Aristotle, but also has innovative and innovative aspects. In this transition, Cartesian doubt plays the role of groundwork and preparation, which must also be addressed.