SECTION II. 



THE term scientific truth could not properly be 

 applied to a mere personal statement of the imme- 

 diate sensation of an individual. Thus, if a man feels 

 hot he cannot doubt the fact of his sensation ; it is a 

 true fact for him, but it is not in itself science. More- 

 over, as Hume very clearly saw, no collection of 

 such sensations could constitute scientific knowledge. 

 Locke had already recognised that such knowledge 

 must be the guide of action ; but the immediate sen- 

 sation can, of itself, give no further guidance than 

 this that action should be continued so long as 

 sensation continues pleasant, and should be inter- 

 mitted when sensation ceases to be pleasant. This 

 elementary guidance appears to be sufficient only for 

 the very simplest organisms ; no animal which 

 attempts to escape from its enemies by flight can 

 be supposed to commence and continue that flight 

 merely because the action is, in itself, pleasant. 



The knowledge which affords effective guidance 

 for action depends upon the combination of sensa- 

 tions ; but what I have called the immediate sensa- 

 tion is in its nature transient, and cannot be combined 

 with other sensations unless they be simultaneous ; 

 therefore the combinations of sensation which consti- 

 c 



