Yes! Descartes has finally reached the first principle; the foundation upon which knowledge rests
He concludes, Cogito ergo sum, “I think, therefore I am” In the very act of thinking, we prove that our minds exist. We can still doubt the body (remember, Descartes’ doubt of sensation and sense experiences), but our minds are necessarily extant at the time we begin to think or doubt This is the foundation upon which Descartes’ then rebuilds the world