This text explores René Descartes' conception of thinking as a substance, contrasting it with the notion of thinking as an activity or performance. According to Descartes, thinking is one of the two finite substances, the other being extension. This dualism leads to a specific philosophical problem regarding error: if true thinking is a substance, then incorrect thinking is essentially a failure to think, reducing the individual to a mere extended thing. Consequently, for a human to think truly means to participate in "thinking itself" as a substance, rather than engaging in an autonomous subjective act. The author argues that in this framework, it is not the individual who thinks in the true sense; rather, the individual aligns their mind with the universal substance of thought. Therefore, the only legitimate form of human cognitive activity becomes mimesis—the imitation of and identification with the substance of thought. This perspective suggests that human agency is secondary to the inherent nature of the thinking substance.