SENSORY AND RATIONAL DISCRIMINATION 123 



sensibility, the sensitiveness belonging to every 

 organism, even the lowest, and the rational power 

 of man, attaining to generalisation from particulars. 

 The former belongs to the star-fish and snail ; the latter 

 belongs to man only. In the first case, we include 

 the lowest life ; in the second, we exclude all but the 

 highest. In the mollusc, 1 organism, function, and 

 experience are at the lowest ; in man, all these are at 

 the highest. Equally sharp is the contrast when 

 activity is contemplated. In the mollusc, activity 

 is correlated with sensibility, its end being the 

 securing of nutriment from the current of water 

 passing through the body. In man, activity is also 

 correlated with sensibility, though on a grander scale ; 

 but there is this difference, that in man activity is 

 largely concerned with attainment of knowledge and 

 of right conduct. Our ultimate question is, has the 

 highest been evolved out of the lowest, through 

 numberless gradations. Our primary problem, here, 

 concerns the difference between sensory discrimination 

 and rational. Contrast is at this point the first 

 requisite for precision. Boldness of outline will abate 

 the difficulties of an inquiry so vast as that presented 

 by comparative biology. If biologists propose to 

 attribute mental power to the mollusc, the dis 

 cussion as to mind begins from the first appearance 

 of life. If biologists propose to attribute mental 

 power only to the higher mammals, there remains 

 a preliminary and more general question, as to the 

 discrimination which is possible to all organism. In 

 any case, ideation must be carried to the rear, while 



1 Carpenter s Mental Physiology, p. 45 ; Calderwood s Relations 

 of Mind and Brain, p. 123. 



