What is the significance of the phrase "Cogito, ergo sum" in the philosophy of Ren Descartes?

The phrase "Cogito, ergo sum" means "I think, therefore I am" in Latin. It is significant in Ren Descartes' philosophy because it represents his foundational belief that the act of thinking proves one's existence. Descartes used this statement to establish a starting point for his philosophical inquiry, emphasizing the importance of self-awareness and rational thought in understanding reality.