"Discourse on Method" by Rene Descartes is a foundational work of modern philosophy that established the importance of reason and rational thought in understanding the world. The book is divided into six parts, each exploring a different aspect of Descartes' philosophy. The key theme of the book is doubt - Descartes argues that we must doubt everything we think we know in order to arrive at a truly certain understanding of reality. This leads to his famous assertion, "Cogito, ergo sum" - "I think, therefore I am".
One concrete criticism of the book is that his methodology of doubting everything may be too extreme and impractical. Descartes' method requires doubting even the most basic and fundamental beliefs, such as the existence of the external world and the reliability of our senses. This extreme doubt can be seen as a form of skepticism that leads to an unproductive cycle of doubting and questioning without ever arriving at a certain conclusion.
However, despite these criticisms, "Discourse on Method" remains an important work that laid the groundwork for modern philosophy. The concept of doubt and the famous assertion "Cogito, ergo sum" continue to be studied and discussed today, making the book a significant contribution to the field of philosophy.