13/13 AN INTRODUCTION TO CYBERNETICS 



Abstractly this selection is identical with having initially a machine 

 with three-valued input : 



and then deciding that the input shall be fixed permanently at jS. 

 (The processes are identical in the sense that if some observer 

 watches only the results of the processes, he cannot tell which has 

 occurred except by reference to other, unmentioned, criteria.) 



In this example, fixing the input at j8 leaves the resulting machine 

 an absolute system, without input. If the result of the selection is 

 to be a machine with input, then the original machine must start 

 with two or more inputs, so that the fixing of one by the act of design- 

 selection leaves the others free for further variation as ordinary 

 inputs. 



The designer'' s act of selecting one model from many is equivalent 

 to some determining factor fixing an input at a permanent value. 



13/13. (This section treats a minor complication.) 



In the examples above, the choice has been between machines 

 whose transformations have had the same set of operands, i.e. the 

 same set of states in the machine. What if the choice were to lie 

 between, say, 



I ^ and j ^ ^ ? 



b a r q r 



Can such a selection be represented by the fixing of an input value? 

 Such a choice might occur in the early stages of design, as when the 

 first decision is made whether the components shall be electronic 

 or hydrauHc. 



In fact this case is contained in the former, and can be represented 

 in it by a mere change of notation. Thus the choice just mentioned 

 can equally be represented as that between /x and v in the (reducible) 

 machine, whose states are couples: 



\ 



f* 



{a,p) ia,q) (a,r) {b,p) (b,q) {b,r) 



