existence. Materialism treated physical bodies and their 
     motions as the primary reality; idealism took it to be spirit 
     or mind; while Cartesian dualism postulated two 
     independent realms: the mental res cogitans  and the 
     material res extensa . For the first two schools there was 
     no difficulty in recognizing unconscious mentality though 
     under other names. To the materialists all mentality was 
     physiological, and the existence of unconscious 
     physiological processes, similar to and influencing 
     thought, was an immediate consequence of the fact that 
     our direct awareness of the processes in our bodies is 
     restricted. And to the idealists all natural processes were 
     the expression of a universal mind or world spirit of which 
     the human individual has no direct knowledge, though it 
     shares, in some degree, the characteristics of human 
     mentality. Thus for the idealists also there was no