THE ULTRASTABLE SYSTEM 



8/10 



is stable in conjunction with all the system's parameter-values 

 (and it is clear by the principle of ultrastability that this must be 

 so, for whether the parameters are at their ' usual ' values or 

 not is irrelevant). The ultrastable system will therefore always 

 produce a set of step-function values which is so related to the 

 particular set of parameter-values that, in conjunction with them, 

 the system is stable. If the parameters have unusual values, 



U 



m 



Time 



Figure 8/10/1 : Three units interacting. At J, units 1 and 2 were con- 

 strained to move together. New step-function values were found which 

 produced stability. These values give stability in conjunction with the 

 constraint, for when it is removed, at R, the system becomes unstable. 



the step-functions will also finish with values that are compen- 

 satingly unusual. To the casual observer this adjustment of the 

 step-function values to the parameter- values may be surprising ; 

 we, however, can see that it is inevitable. 



The fact is demonstrable on the homeostat. After the machine 

 was completed, some ' unusual ' complications were imposed on 

 it (' unusual ' in the sense that they were not thought of till 

 the machine had been built), and the machine was then tested 

 to see how it would succeed in finding a stable field when 

 affected by the peculiar complications. One such test was 



101 H 



