8/11 



THE HOMEOSTAT 



Now the ultrastable system proceeds to a terminal field which 

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

 (and it is clear 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-mechanism 

 values which is so related to the particular set of parameter- values 

 that, in conjunction with them, the system is stable. If the para- 

 meters have unusual values, the step-mechanisms will also finish 

 with values that are compensatingly unusual. To the casual 

 observer this adjustment of the step-mechanism 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 made by joining 



U 



m 



Time 



Figure 8/11/1 : Three units interacting. At J, units 1 and 2 were con- 

 strained to move together. New step-mechanism 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. 



117 



