SENSATION AND PERCEPTION 117 



change in the latter, the former assumes definite values given by 

 the function, /. We may say, therefore, that we only have 

 sensations when the " reasons " for them, that is, certain physical 

 events, occur. But we may not say that the symbolism that 

 describes all inorganic happenings also describes the relation 

 between a sensation and its physical antecedents — that this 

 relation is not that one characteristic of inorganic happening is 

 shown when we know that physical events may, or may not, be 

 followed by sensation. 



Therefore we have sensations when, in certain circumstances, 

 physical agencies react with our organs of reception, but the 

 relation between these terms involves the " mind-body " problem 

 and is quite unknown to us in spite of all that has been written 

 upon it. 



43^. Pure Sensation is not experienced by us. In our 

 ordinary traffic with the world we have at the same moment many 

 sensations and we cannot avoid thinking about them. Probably 

 we approximate to pure sensation at times. Probably a dog lying 

 on a mat in front of the fire feels warm — supported — comfortable, 

 etc. — all at once. But a man sitting in an easy chair in the same 

 conditions cannot, as a rule, avoid reflecting upon his sensations 

 — and in these reflections he has new states of consciousness which 

 come from his thinking. Sensation, then, is always elaborated 

 into perceptions. 



43c. Classifiable Sensations. When we think about, and 

 make experiments with sensations and their concomitants, and 

 when we study artificial receptors we can make a rough classifica- 

 tion of sensations. 



i. Associated with the distance-receptors. 



Vision. Visual organs. Mere light and shade and dark- 

 ness in lower animals. Seeing form and colour in man. 

 Probably seeing form but not colour in many higher 

 animals. 



Hearing. The auditory organs. Sound with intensity 

 and pitch in man and higher vertebrates. But not always 

 pitch in the lower animals. 



Heat. Temperature organs in the skin afi^ected by radia- 

 tion. 



a. Associated with the ?iear-receptors. 



Smell. Olfactory organs. Decadent in man and 



