"(T)he basis of the philosophy of Descartes is radically different from that of the ancient Greek philosophers," Heisenberg notes. "Here the starting point is not a fundamental principle or substance, but the attempt of a fundamental knowledge. And Descartes realizes that what we know about our mind is more certain than what we know about the outer world. But already his starting point with the "triangle" God-World-I simplifies in a dangerous way for further reasoning.""If one follows the great difficulty which even eminent scientists like Einstein had in understanding the Copenhagen interpretation of quantum theory," Heisenberg remarks, "one can trace the roots of this difficulty to the Cartesian partition. This partition has penetrated deeply into the human mind during the three centuries following Descartes and it will take a long time for it to be replaced by a really different attitude toward the problem of reality."
"The division between matter and mind or between soul and body, which had started in Plato's philosophy, is now complete. God is separated both from the I and from the world. God in fact is raised so high above the world and men that He finally appears in the philosophy of Descartes only as a common point of reference that establishes the relation between the I and the world."
"If one uses the the fundamental concepts of Descartes at all," Heisenberg continues, "it is essential that God is in the world and in the I and it is also essential that the I cannot be really separated from the world. Of course Descartes knew the indisputable necessity of the connection, but philosophy and natural science in the following period developed on on the basis of the polarity between the "res cogitans" and "res extensa." The influence of the Cartesian division on human thought in the following centuries can hardly be overestimated, but it is just in this division which we have to criticize later from the development of physics in our time."
[Heisenberg, "Physics and Philosophy," pp. 52-53]