188 THE MECHANISM OF LIFE 



the activity is to be a new one, and cannot therefore make use of 

 any established cerebral and nervous paths). The memory is 

 applied in a number of ways, and if we may compare mental 

 operations with certain modes of animal acting, we might think 

 about them as beginning by a method of trial and error. The 

 memories of past stimuli and their responses are tried in one way 

 or other until a way is discovered that is likely to be successful. 

 The cerebral paths are then discovered or made, and the response 

 is effected. The mental operation that was employed and which 

 succeeded is thus an acquired one, and we must suppose that it 

 is transmitted by heredity. 



These transmitted mental operations whereby pure memory is 

 utilised in the elaboration of new activities are the Kantian 

 categories. 



Apparently, then, we think (that is, employ the categories) 

 because we have acted, or because we are about to do so. That 

 means that we ought to show that all thinking, all intellectual 

 constructions, are actual, or nascent, or virtual ways in which 

 we are acting, or might act upon the outer world. It would not 

 be difficult to show that this is really true, that Newton, for 

 instance, in deducing the law of gravitation, was virtually acting 

 upon the earth-moon system. He could not, of course, move the 

 moon in its orbit with a certain velocity, nor could he pull it 

 towards him, but he could produce accelerations in the velocity 

 of an apple, and he could exert such muscular force as would 

 counteract the acceleration of the latter body when it was free 

 to fall towards the earth. Now, by " producing " this personal 

 power of acting he could imagine himself moving the moon in its 

 orbit, and at the same time pulling it towards the earth in such 

 a way that the observed movements of our satellite were as they 

 would have been if the action had been a real instead of a virtual 

 one. Something like this occurs whenever we think, even in the 

 most abstract way: we do not actually do things, but we " set the 

 points," so to speak, in order that certain actions might occur if 

 it were to become practicable to effect them. 



Space and Time.* 



There are, said Kant, the categories of quantity, quality, 

 relation, and modality; these are ways in which we think about 

 the objects of sensible experience. There are also the " pure 



* See also Appendix II. 



