86 Physical Heredity and Social Trans77iission 



does not understand my position, I think. I differ from him 

 both in the psychology of voluntary accommodations of 

 movement and in the view that consciousness is a sort of 

 force directing brain currents in one way or another (for 

 nothing short of a force could release or direct brain cur- 

 rents). The principle of dynamogenesis was cited in this 

 form, i.c.y 'the thought of a movement tends to discharge 

 motor energy into the channels as near as may be to those 

 necessary for that movement' (above p. 55-56). This prin- 

 ciple covers two facts. First, that no movement can be 

 voluntarily carried out which has not itself been performed 

 before and left traces of some sort in memory. These traces 

 must come up in mind when its performance is again in- 

 tended.i And second (and in consequence of this), that no 

 act, whatever, can be performed by consciousness by will- 

 ing movements which have never been performed before. 

 It follows that we cannot say that consciousness, by select- 

 ing new adjustments beforehand, can make the muscles 

 perform them. The most that many recent psychologists 

 are inclined to claim is that by the attention one or other 

 of alternative movements which have been performed 

 before (or combinations of them) may be performed again ; 

 in other words, selection is among old alternative move- 

 ments. Ikit this is not what Professor Cope seems to 

 mean, nor what his theory requires. His theory requires 

 the acquisition of new movements, new accommodations to 



1 This is formulated in the principle of * Kinoesthetic Equivalents,' defined 

 in the writer's Diet, of Philos. and Psychol, as follows : * any mental content 

 of the kina.'sthetic order [/.^., representing earlier experiences of movement] 

 which is adef[uatc to secure the voluntary performance of a movement. . . . 

 The term Cfiuivalent is recommended to sum up the formulation that unless a 

 kin.t-sthctic content " etiuivalent " to a movement be reinstated in conscious- 

 ness the voluntary performance of that movement is impossible.' 



