6 THE ORIGIN OF HUMAN REASON. 



is essentially distinct from that of any mere animal, 

 there is none the less abundant evidence that certain 

 physical conditions are necessary for its external mani- 

 festation. In the absence of those conditions it may, 

 as in sleep, remain latent. That often, when not 

 externally apparent, it may for all that really persist in 

 a latent condition, is plainly shown us by the fact that 

 it can and does become subsequently manifest — as on 

 waking — when the needful conditions have been supplied, 

 as, e.g., through sufficient rest. 



(2) Each human being is a true unity which possesses, 

 simultaneously, the powers of two natures — one animal 

 and the other rational — both sets of powers * co-operating 

 in the whole mental life of each individual. We can- 

 not, therefore, separate, for examination, our intellect 

 from our sensuous activity, while our intellectual nature 

 modifies the exercise of even our mere sensitivity. 

 Nevertheless we can sufficiently distinguish the qualities 

 of either set of faculties to be aware of the great differ- 

 ence which exists between them. 



(3) We know, both by common sense and careful 

 observation, that brutes do not make manifest externally 

 an unequivocally intellectual nature. But though we 

 know that such manifestations do not occur, we cannot 

 know all that animals are or may be. We cannot, there- 

 fore, venture positively to affirm that, in the absence of 



♦ In our work "On Truth" (Kegan Paul, Trench and Co., 1889) 

 we have described at length— pp. 178-223— both our higher and 

 our lower mental powers. We shall be compelled again and again 

 to refer our readers to this work, which was sent to press before 

 that of Mr. Romanes appeared. Had it not been so sent the 

 present volume would have been superfluous. 



