Chapter 11 



REQUISITE VARIETY 



11/1. In the previous chapter we considered regulation from the 

 biological point of view, taking it as something sufficiently well 

 understood. In this chapter we shall examine the process of regula- 

 tion itself, with the aim of finding out exactly what is involved and 

 implied. In particular we shall develop ways of measuring the 

 amount or degree of regulation achieved, and we shall show that 

 this amount has an upper limit. 



11/2. The subject of regulation is very wide in its applications, 

 covering as it does most of the activities in physiology, sociology, 

 ecology, economics, and much of the activities in almost every 

 branch of science and life. Further, the types of regulator that exist 

 are almost bewildering in their variety. One way of treating the 

 subject would be to deal seriatim with the various types; and chapter 

 12 will, in fact, indicate them. In this chapter, however, we shall be 

 attempting to get at the core of the subject — to find what is common 

 to all. 



What is common to all regulators, however, is not, at first sight, 

 much like any particular form. We will therefore start anew in the 

 next section, making no explicit reference to what has gone before. 

 Only after the new subject has been sufficiently developed will we 

 begin to consider any relation it may have to regulation. 



11/3. Play and outcome. Let us therefore forget all about regula- 

 tion and simply suppose that we are watching two players, R and D, 

 who are engaged in a game. We shall follow the fortunes of R, who 

 is attempting to score an a. The rules are as follows. They have 

 before them Table 11/3/1, which can be seen by both: 



