THE MACHINE WITH INPUT 4/17 



At this minute of writing, the Laughter and Singing are 

 both sounding. Please tell ine what manipulations of incense 

 and organ I should make to get the house quiet, and to keep 

 it so. 



(Hint: Compare Ex. 4/1/4.) 



Ex. 2 : (Continued.) Does the Singing have an immediate effect on the Laughter ? 



Ex. 3: (Continued.) Does the incense have an immediate effect on the Singing? 



Ex. 4: (Continued.) Deduce the diagram of immediate effects of this machine 

 with input (with two parameters and two variables). 



THE VERY LARGE SYSTEM 



4/16. Up till now, the systems considered have all seemed fairly 

 simple, and it has been assumed that at all times we have understood 

 them in all detail. Cybernetics, however, looks forward to being 

 able to handle systems of vastly greater complexity — computing 

 machines, nervous systems, societies. Let us, then, consider how 

 the methods developed so far are to be used or modified when the 

 system is very large. 



4/17. What is meant by its "size" needs clarification, for we are 

 not here concerned with mere mass. The sun and the earth form 

 only a "small" system to us, for astronomically they have only 

 twelve degrees of freedom. Rather, we refer to the system's 

 complexity. But what does that mean here? If our dynamic 

 system were a native family of five persons, would we regard it 

 as made of 5 parts, and therefore simple, or as of lO^^ atoms, and 

 therefore very complex ? 



In the concepts of cybernetics, a system's "largeness" must refer 

 to the number of distinctions made: either to the number of states 

 available or, if its states are defined by a vector, to the number of 

 components in the vector (i.e. to the number of its variables or of its 

 degrees of freedom, S.7/13). The two measures are correlated, for 

 if other things are equal, the addition of extra variables will make 

 possible extra states. A system may also be made larger from our 

 functional point of view if, the number of variables being fixed, each 

 is measured more precisely, so as to make it show more distinguish- 

 able states. We shall not, however, be much interested in any exact 

 measure of largeness on some particular definition ; rather we shall 

 refer to a relation between the system and some definite, given, 

 observer who is going to try to study or control it. In this book I 



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