214 MENTAL EVOLUTION IN MAN. 



untold thousands of years made no advance upon the 

 chipping of flints, we cannot say that, when gauged by the 

 practical test of efficiency or adaptation, the one appears to 

 be very much in advance of the other. Or, if we remember 

 that these same men never hit upon the simple expedient of 

 attaching a chipped flint to a handle, so as to make a hatchet 

 out of a chisel,* it cannot be said that in the matter of 

 mechanical discovery early conceptual life displayed any 

 great advance upon the high receptual life of my cebus. 

 Nevertheless, I have allowed — nay insisted — that no matter 

 how elaborate the structure of receptual knowledge may be, 

 or how wonderful the adaptive action it may prompt, a 

 "practical inference" or "receptual judgment" is always 

 separated from a conceptual inference or true judgment by 

 the immense distinction that it is not itself an object of 

 knowledge. No doubt it is a marvellous fact that by means 

 of receptual knowledge alone a monkey should be able to 

 di\'ine the mechanical principle of a screiu, and afterwards 

 apply his discovery to all cases of screws. But even here 

 there is nothing to show that the monkey ever thought about 

 the principle as a principle ; indeed, we may rest well assured 

 that he cannot possibly have done so, seeing that he was not 

 in possession of the intellectual instruments — and, therefore, 

 of the antecedent co7iditions — requisite for the purpose. All 

 that the monkey did was to perceive receptually certain 

 analogies : but he did not conceive them, or constitute them 

 objects of thought as analogies. He was, therefore, unable 

 to predicate the discovery he had made, or to set before his 

 own mind as knowledge the knowledge which he had gained. 

 Or, to take another illustration, the bird which saw three 

 men go into a building, and inferred that one must still have 

 remained when only two came out, conducted the inference 

 receptually : the only data she had were those supplied by 

 differential sense-perceptions. But although these data were 



* "Of all the neolithic implements the axe was by far the most important. It 

 was by the axe that man achieved his greatest victory over nature " (Boyd Uawkins, 

 Early Alan in Britain, p. 274), 



