Chapter 7 



QUANTITY OF VARIETY 



7/1. In Part I we considered the main properties of the machine, 

 usually with the assumption that we had before us the actual thing, 

 about which we would make some definite statement, with reference 

 to what it is doing here and now. To progress in cybernetics, 

 however, we shall have to extend our range of consideration. The 

 fundamental questions in regulation and control can be answered 

 only when we are able to consider the broader set of what it might 

 do, when "might" is given some exact specification. 



Throughout Part II, therefore, we shall be considering always 

 a set of possibilities. The study will lead us into the subjects of 

 information and communication, and how they are coded in their 

 passages through mechanism. This study is essential for the 

 thorough understanding of regulation and control. We shall start 

 from the most elementary or basic considerations possible. 



7/2. A second reason for considering a set of possibilities is that 

 science is little interested in some fact that is valid only for a single 

 experiment, conducted on a single day; it seeks always for generalisa- 

 tions, statements that shall be true for all of a set of experiments, 

 conducted in a variety of laboratories and on a variety of occasions. 

 Galileo's discovery of the law of the pendulum would have been of 

 little interest had it been valid only for that pendulum on that after- 

 noon. Its great importance is due precisely to the fact that it is 

 true over a great range of space and time and materials. Science 

 looks for the repetitive (S.7/15). 



7/3. This fact, that it is the set that science refers to, is often ob- 

 scured by a manner of speech. "The chloride ion . . .", says the 

 lecturer, when clearly he means his statement to apply to all chloride 

 ions. So we get references to the petrol engine, the growing child, 

 the chronic drunkard, and to other objects in the singular, when the 

 reference is in fact to the set of all such objects. 



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