CONDITIONS NECESSARY FOR ACQUIRING IDEAS. 47 



ments or pairs of perceptions together, in order to obtain 

 an impression of identity or difference. 



Ideas may be either strong or feeble, distinct or indis- 

 tinct. The strength and distinctness of an idea depends 

 upon the nature of the idea, the state of education of the 

 mind, the vividness of the impression, or the perfection of 

 the memory. Strong impressions produce the most vivid 

 ideas. The more vivid also the original impression, and 

 the more perfect the action of the memory, the stronger 

 and more distinct is the idea. The clearest ideas are 

 those of simple number, because they are the most definite. 

 General and abstruse ideas usually produce much less 

 vivid impressions than individual and superficial ones ; 

 but they have stronger effects upon educated than upon 

 uneducated minds. Superficial ideas have greater effect 

 upon uneducated persons, because they are the most easily 

 perceived, and require the least intellectual exertion. Our 

 ideas of all great general truths are extremely inadequate, 

 in consequence of the abstract and extensive nature of the 

 truths which they represent. 



Perception of ideas requires time. When we first 

 realise the idea of an object which is entirely new to us, 

 we cannot at once distinguish between its different parts 

 or properties, we cannot immediately perceive what is 

 essential to it, or what is accidental or coincident, nor into 

 what parts or other ideas it may be divided ; nor can we 

 obtain so distinct an impression. Confusion of ideas often 

 arises also from the presence of a multiplicity of conscious 

 impressions, from insufficient time to realise them, or from 

 the intrusion of incongruous ones, and sometimes from a 

 deficiency of mental control. Complex, and especially 

 panoramic ideas, are often very inadequate, and so also 

 are simpler ideas of extremely large or small objects. 

 Dull brains produce obscure ideas. Different ideas also 



