GENERAL SUMMARY AND CONCLUDING REMARKS. 39I 



the human mind presents to actual observation a process of 

 g^radual development, extendin^^ from infancy to manhood. 

 For it is thus shown to be a matter of observable fact that, 

 whatever may have been the origin or the history of human 

 intelligence in the pa>t, as it now exists — or, rather, as in 

 every individual case it now comes into existence — it proves 

 itself to be no exception to the general law of evolution : it 

 unquestionably does admit of gradual growth from a zero 

 level, and without such a gradual growth we have no 

 evidence of its becoming. Furthermore, so long as it is 

 passing through the lower stages of this growth, the human 

 mind ascends through a scale of faculties which are parallel 

 with those that are permanently presented by what I have 

 termed the psychological species of the animal kingdom — a 

 general fact which tends most strongly to prove that, at all 

 events up to the time when the distinctively human qualities 

 of ideation are attained, no difference of kind is apparent 

 between human and brute psychology. Lastly, not only 

 in the individual, but also in the race, the phenomena of 

 mental evolution are conspicuous — so far, at least, as the 

 records of the human race extend. Whether we have regard 

 to actual history, to tradition, to antiquarian remains, or 

 flint implements, we obtain uniform evidence of a continuous 

 process of upward development, which is thus seen to be 

 as characteristic of those additional attributes wherein the 

 human mind now surpasses that of any other species as it 

 is of those attributes which it shares with other species. 

 Therefore, if the process of mental evolution was interrupted 

 between the anthropoid apes and primitive man during 

 the pre-historic period of which we have no record, it must 

 again have been resumed with primitive man, after which 

 it must have continued as uninterruptedly in the human 

 species as it previously did in the animal species. This, to 

 say the least, is a most improbable supposition. The law of 

 continuity is proved to apply on both sides of a ps)'chological 

 interval, where there happens to be a necessary absence of 

 historical information. Yet we are asked to believe that, in 

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