CHAP. XII.] AND PERCEPTION. 185 



These two components exist in every Sensation, though, 

 as Sir William Hamilton contends, in an inverse ratio. 

 The formula of the one is I feel, the formula of the other 

 I knoiv. The one is represented by what has heen termed 

 ' Sensation proper,' and, in its higher developments, by 

 Emotions, and Moral Sentiments ; the other by ' Percep- 

 tion proper,' and, in its higher developments, by Judg- 

 ment, Imagination, Conception, Reasoning, or the more 

 purely Intellectual Processes. 



There is, indeed, a third aspect of Sensation or Percep- 

 tion, which has not yet been mentioned, though it seems 

 to be one of great importance in helping to determine the 

 Development of Nervous Structures, and the correlative 

 increasing complexity of Mental Phenomena. This is to 

 be found in that exercise of Volition or Will which enters 

 into every Perception under the form of Attention. Nor 

 must it be here forgotten that in still another way are 

 Sensations related to Volitions. The pleasures and pains 

 of Sense, either actually present or represented in Idea, 

 seem unquestionably to constitute the subjective sides of 

 those neural processes which most frequently issue in the 

 so-called Volitional Movements. But this subject will 

 be more fully considered in a later chapter. 



It is of great importance, however, here to note that 

 Intelligence, Sensation, Emotion, and Volition are mental 

 processes, the primary stages of which are dependent 

 upon, and inseparably connected with, different modes or 

 aspects of the functional activity of the Perceptive Centres; 

 and that this conclusion at which we have arrived is one 

 which will be found to be quite harmonious with the dicta 

 of philosophers in regard to human Psychology. Thus 

 Sir William Hamilton says*: " In every, the simplest, 

 modifications of Mind, Knowledge, Feeling, and Desire 01 

 * " Lectures on Metaphysics," vol. i. p. 188. 



