v THE MENTAL PHENOMENA OF ANIMALS 127 



and it is conceivable that these may at first exist, 

 without any power of reproducing them, as 

 memories; and, consequently, without ideation. 

 Still higher, an apparatus of correlation may be 

 superadded, until, as all these organs become more 

 developed, the condition of the highest speechless 

 animals is attained. 



It is a remarkable example of Hume's sagacity 

 that he perceived the importance of a branch of 

 science which, even now, can hardly be said to 

 exist; and that, in a remarkable passage, he 

 sketches in bold outlines the chief features of com- 

 parative psychology. 



"... any theory, by which we explain the operations of 

 the understanding, or the origin and connection of the pas- 

 sions in man, will acquire additional authority if we find 

 that the same theory is requisite to explain the same phenom- 

 ena in all other animals. We shall make trial of this with 

 regard to the hypothesis by which we have, in the foregoing 

 discourse, endeavoured to account for all experimental rea- 

 sonings ; and it is hoped that this new point of view will 

 serve to confirm all our former observations. 



" First, it seems evident that animals, as well as men, 

 learn many things from experience, and infer that the same 

 events will always follow from the same causes. By this 

 principle they become acquainted with the more obvious 

 properties of external objects, and gradually, from their 

 birth, treasure up a knowledge of the nature of fire, water, 

 earth, stones, heights, depths, &c., and of the effects which 

 result from their operation. The ignorance and inexperi- 

 ence of the young are here plainly distinguishable from the 

 cunning and sagacity of the old, who have learned, by long 

 observation, to avoid what hurt them, and pursue what 

 gave ease or pleasure. A horse that has been accustomed 



