758 THE PHYSIOLOGY OF CONSCIOUS STATES [CH. LII. 



Consequently, instead of stating that physiological activity is the 

 cause of mental (or psychical) activity, it is more satisfactory to 

 assume that the two activities run parallel with one another, and to 

 recognise that the nature of their relation is unknown. This con- 

 ception of psycho-physical parallelism affords the physiologist by far 

 the best working hypothesis. 



It leaves unanswered the great question whether brain ever acts 

 on mind, or mind on the brain which of the two is the master or 

 the servant of the other. It merely implies that a change in nerve 

 substance underlies every psychical change ; and it bids the physio- 

 logist investigate the functions of the nervous system, and determine 

 what structures are called into activity in the development of 

 various conscious states. 



We must recognise that, however completely we may one day 

 have mapped out the functions of the various parts of the brain, we 

 shall nevertheless not have approached a step nearer towards under- 

 standing the relation between the data of physiological and psychical 

 activity. If we knew the function of every nerve cell of the body, 

 the gap between the material and the mental would not be a bit less 

 wide. Just as a ray of light cannot see itself, so we cannot expect 

 to understand states of consciousness from a mere study of cerebral 

 function. 



It is therefore imperative to avoid confusion between the two 

 aspects involved in this psycho-physical parallelism. The psychical 

 is one language, the physical (i.e. the physiological) is another; 

 and the two vocabularies must be kept distinct from one another. 

 Psychology and physiology stand in the relation of an object and 

 its mirrored reflection. To confound object and image to speak, for 

 instance, of a sensation (instead of an impulse) being transmitted 

 along a nerve-fibre, is to blur and to confuse two distinct sciences. 



The psychologist distinguishes three modes in which conscious- 

 ness is manifested. These are (1) the cognitive, (2) the affective, 

 and (3) the conative modes. Through the cognitive mode we become 

 aware of the object thought of. Owing to the affective mode, our 

 state of consciousness is toned with pleasure, indifference, or dis- 

 pleasure. The conative mode manifests itself as a striving or " felt 

 tendency" towards an end. In every state of consciousness these 

 three modes are present, but their relative prominence is always 

 different. For example, in perception, in memory, or imagination, the 

 cognitive element is to the fore; in love, sorrow, or doubt, the 

 affective element predominates ; while in intense desire, the conative 

 element is most easily recognisable. Into the physiology of affection 

 and conation we shall not enter here. They receive adequate atten- 

 tion in books devoted to physiological and experimental psychology. 

 But a conscious state implies also a contrast between what is 



