7/25 THE ULTRASTABLE SYSTEM 



the line of behaviour from Z is stable with regard to the region, 

 so the representative point moves to the state of equilibrium and 

 stops there. No further critical states are met, no further step- 

 functions change value, and therefore no further changes of field 

 take place. From now on, if the field of the main variables is 

 examined, it will be found to be stable. The organism, if dis- 

 placed moderately from the state of equilibrium, will return to it, 

 thus demonstrating the various evidences of adaptation noticed 

 in Chapter 5. 



7/24. This field, and this state of equilibrium, will, under con- 

 stant external conditions, persist indefinitely. If the system is 

 now subjected to occasional small impulsive disturbances (that 

 simply displace the representative point as in S. 6/5) the whole 

 will as often display its stability ; in the same action, the organismal 

 part will display that it now possesses an ' adapted ' mechanism 

 for dealing with the environmental part. 



During the description of the previous section, much notice was 

 taken of the trials and failures, and field IV seemed to be only 

 the end of a succession of failures. We thus tended to lose a 

 sense of proportion ; for what is really important to the living and 

 learning organism is the great number of times on which it can 

 display that it has already achieved adaptation; in fact, unless 

 the circumstances allow this number to be fairly large and the 

 number of trial-failures to be fairly small, there is no gain to the 

 organism in having a brain that can learn. 



7/25. It should be noticed that the second feedback makes, for 

 its success, no demands either on the construction of the reacting 

 part R or on the successive values that are taken by S. Another 

 way of saying this is to say that the mechanism is in no way put 

 out of order if R is initially constructed at random or if the successive 

 values at S occur at random. (The meaning of ' constructed at 

 random ' is given in S. 13/1.) 



Such a construction at random probably occurs to some extent 

 in the nervous system, where the ultimate units (dendrons, pieds 

 terminaux, protein molecules perhaps) occur in numbers far too 

 great for their determination by the gene-pattern in detail (S. 1/9). 

 In the formation of the embryo brain, therefore, some of the final 

 details may be determined by the accidents of local minutiae — 



97 



