46 GENERAL VIEW AND BASIS OF SCIENTIFIC RESEARCH. 



object to that of many, and .on to panoramic conceptions 

 formed by the mental association of numerous ideas. 

 Those of unity, existence, and succession are simple ones, 

 and the simplest are those of definite units or numbers. 

 Even a simple idea is often an abstract result of many 

 repetitions of similar impressions ; and a complex one is 

 a compendium of impressions obtained usually through 

 several senses. A complex existence may excite in us 

 either many single ideas of its different constituents or 

 attributes, a single abstract idea of its essential portion, 

 or a complex panoramic idea of all. The most complete 

 perception usually requires the aid, more or less, of all the 

 senses and intellectual powers. Simple ideas are often 

 formed automatically, and so also are many complex ones ; 

 but the most complex, abstruse, or unfamiliar ideas require 

 the aid of strong attention to intensify their strength and 

 enable us to perceive them, and the conception of them 

 indicates the limits of man's ideational powers. Strong 

 volitional thought is also much more exhausting than 

 that which is automatic. According to Sir W. Hamil- 

 ton, we can only retain in our mind about six ideas simul- 

 taneously. ( He only sees well who sees the whole in the 

 parts, and the parts in the whole ' (Lavater). 



Nearly all our mental activity may be viewed as con- 

 sisting of conceptions and observations of different degrees 

 of complexity. Thus in the act of simple perception, we 

 conceive a single idea, in order to realise it ; in forming a 

 judgment we conceive and observe two co-existing percep- 

 tions or ideas, in order to obtain an impression that the 

 one belongs to the other, as, for instance, redness belongs 

 to copper, &c ; in making a comparison, we conceive and 

 observe two ideas together, in order to obtain an impres- 

 sion of similarity or difference ; and, in drawing an 

 inference, we conceive, observe, and compare two judg- 



