72 lotka: discontinuous evolution 



Now A's success will evidently depend on two factors: 

 Firstly on his determination and skill in the selection of a suitable 

 function; and secondly on the precision with which he attains 

 the functional relation aimed at. This precision in turn depends 

 on two factors: on the one hand on the accuracy of his sense 

 organs (receptors), as measured for example by the frequency 

 curve of his observational errors; on the other hand the pre- 

 cision of A's fencing depends on the agility with which his body 

 and limbs (effectors) carry out the actions aimed at, i.e., those 

 corresponding to the function selected. 



Leaving now our simile, 4 and considering the actual case of a 

 living organism, such as man, we observe that thruout all his 

 activities there runs the so-called " sensory-motor circuit," which 

 comprises the following steps: 



1. The external world is " represented " (in the mathematical 

 sense) 5 in the individual. This is effected partly by the sense 

 organs (receptors), and partly also with the assistance of the 

 thinking organ, which, by logical argument, further develops 

 the representation formed directly by the sense perceptions. 



2. The representation of the external world so obtained 

 calls out another representation of a " modified external world." 

 (The modification may involve both the external world and the 

 individual.) If this modified " representation " be a subject of 

 consciousness in the individual, we recognise it as a "desire," 

 "purpose," or "intention." If several alternatives of this kind 

 are presented, in general one of these is selected. If this choice 

 is made by a conscious process, it is determined by a faculty 

 which may be termed the "judgment of value" of the individual. 



3. The third and terminal step in the circuit is an "action" 

 of the individual, whereby the external world is so modified as 

 to, correspond with greater or less accuracy to the "modified 

 representation" of the external world, which we noted under 

 (2). At this step also, as in (1), thought-processes may assist in 



4 This simile is of course incomplete in so far as we have supposed A to remain 

 purely on the defensive, whereas the typical living organism must necessarily 

 make active attack. This does not, however, materially affect the argument, 

 since the same principles apply to its actions in either attitude. 



5 The German word "abgebildet" is particularly expressive. 



