Final answer:
According to Descartes, the mark of the Cogito is its certainty and clarity.
Step-by-step explanation:
According to Descartes, the mark of the Cogito is its certainty and clarity. Descartes famously stated, "I think, therefore I am," which means that the act of thinking confirms one's existence. This statement is considered the foundation of Descartes' philosophy and the starting point for his argument for the existence of the mind as a separate entity from the body.