6/10 PARAMETERS 



of equilibrium at (3, 1, 5). So, the whole's being at a state of 

 equilibrium implies that each part must be at a state of equilibrium, 

 in the conditions provided (at its parameters) by the other parts. 



Conversely, suppose A is in equilibrium at state (7, 2) when 

 its parameters have the values (3, 1, 5); and that B is in equi- 

 librium at state (3, 1, 5) when its parameters are at (7, 2). It 

 follows that the whole will have a state of equilibrium at the 

 state (7, 2, 3, 1, 5), for at this state neither A nor B can change. 



To sum up : That a whole dynamic system should be in equilibrium 

 at a particular state it is necessary and sufficient that each part should 

 be in equilibrium at that state, in the conditions given to it by the 

 other parts. 



6/9. Suppose now that a whole, made by joining parts, is moving 

 along a line of behaviour. Suppose the line of behaviour meets a 

 state that is one of equilibrium for one part (in the conditions 

 given at that moment by the others) but not equilibrial for the 

 other parts. The part in equilibrium will stop, momentarily; 

 but the other parts, not in equilibrium, will change their states 

 and will thereby change the conditions of the part in equilibrium. 

 Usually the change of conditions (change of parameter- values) 

 will make the state no longer one of equilibrium: so the part that 

 stopped willl now start moving again. 



Clearly, at any state of the whole, if a single part is not at 

 equilibrium (even though the remainder are) this part will change, 

 will provide new conditions for the other parts, will thus start 

 them moving again, and will thus prevent that state from being 

 one of equilibrium for the whole. As equilibrium of the whole 

 requires that all the parts be in equilibrium, we can say (meta- 

 phorically) that every part has a power of veto over the states of 

 equilibrium of the whole. 



6/10. The importance of this fact can now be indicated. By 

 this fact each part acts selectively towards the set of possible 

 equilibria of the whole. Since Chapter 1 we have been looking 

 for some factor that can be both mechanistic and also selective. 

 The next chapter will show this factor in action. 



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