CHAPTER 2 



Dynamic Systems 



2/1. In the previous chapter we have repeatedly used the con- 

 cepts of a system, of parts in a whole, of the system's behaviour, 

 and of its changes of behaviour. These concepts are fundamental 

 and must be properly defined. Accurate definition at this stage 

 is of the highest importance, for any vagueness here will infect 

 all the subsequent discussion ; and as we shall have to enter the 

 realm where the physical and the psychological meet, a realm 

 where the experience of centuries has found innumerable possi- 

 bilities of confusion, we shall have to proceed with unusual 

 caution. 



We start by assuming that we have before us some dynamic 

 system, i.e. something that may change with time. We wish to 

 study it. It will be referred to as the ' machine ', but the word 

 must be understood in the widest possible sense, for no restriction 

 is implied other than that it should be objective. 



2/2. As we shall be more concerned in this chapter with prin- 

 ciples than with practice, we shall be concerned chiefly with 

 constructing a method. When constructed, it must satisfy these 

 axiomatic demands: — (1) Its procedure for obtaining informa- 

 tion must be wholly objective. (2) It must obtain its information 

 solely from the ' machine ', no other source being permitted. 

 (3) It must be applicable, at least in principle, to all material 

 4 machines ', whether animate or inanimate. (4) It must be 

 precisely defined. 



The actual form developed may appear to the practical worker 

 to be clumsy and inferior to methods already in use ; it probably 

 is. But it is not intended to compete with the many specialised 

 methods already in use. Such methods are usually adapted to a 

 particular class of dynamic systems : electronic circuits, rats in 

 mazes, solutions of reacting chemical substances, automatic 

 pilots, or heart-lung preparations. The method proposed here 



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