320 MENTAL EVOLUTION IN ANIMALS. 



ratios, which are themselves more or less elaborated percepts 

 formed out of simpler percepts, or percepts lying nearer to the 

 immediate data of sensation. Thus, universally ratiocination 

 may be considered as the higher development of perception ; 

 for at no point can we draw the line and say that the two are 

 distinct. In other words, a perception is always in its essen- 

 tial nature what logicians term a conclusion, whether it has 

 reference to the simplest memory of a past sensation or to the 

 highest product of abstract thought. For when the highest 

 product of abstract thought is analyzed, the ultimate elements 

 must always be found to consist in material given directly by 

 the senses ; and every stage in the symbolic construction of 

 ideas in which the process of abstraction consists, depends 

 upon acts of perception taking place in the lower stages. 

 True it is that these acts of perception here have reference to 

 the symbols of ideas, which may themselves be far removed 

 from the simple and immediate memories of past sensations ; 

 but as we can nowhere draw the line between perception of 

 the one order and perception of the other, we ought to recog- 

 nize that in the case of this faculty there is nowhere any 

 difference in kind, although everywhere a difference in degree : 

 or, otherwise stated, intellectual processes which culminate in 

 symbolic reasoning are everywhere processes of cognition, 

 and of these processes the term perception is a generic name. 



But having thus shown that in my opinion there is no 

 real break between cognition of the lowest and of the highest 

 order, I must next show at what places I think it is conve- 

 nient, for the sake of historical description, to mark off what 

 I may term conventional stages in the development of cog- 

 nition. This I have already done for the lower stages of such 

 development in my chapter on Perception, where it was 

 shown that the first stage consists in merely perceiving an 

 external object as an external object, the next stage in recog- 

 nizing the simplest qualities of an object, the third stage in 

 mentally grouping objects with reference to their perceived 

 qualities or relations, and the fourth stage in inferring un- 

 perceived qualities or relations from perceived ones — as when 

 on hearing a growl I immediately infer the presence of a 

 dangerous dog. 



Now from this it is apparent that the process of Inference, 

 with which we are in this chapter concerned, is never in its 

 earlier or least developed, stages a process of conscious com- 



