13/3 AN INTRODUCTION TO CYBERNETICS 



13/3. Before we proceed we should notice that when the system is 

 very large the distinction between D, the source of the disturbances, 

 and T, the system that yields the outcome, may be somewhat vague, 

 in the sense that the boundary can often be drawn in a variety of 

 ways that are equally satisfactory. 



This flexibihty is particularly well-marked among the systems that 

 occur on this earth (for the terrestrial systems tend markedly to have 

 certain general characteristics). On this earth, the whole dynamic 

 biological and ecological system tends to consist of many sub- 

 systems loosely coupled (S.4/20); and the sub-systems themselves 

 tend to consist of yet smaller systems, again more closely coupled 

 internally yet less closely coupled between one another; and so on. 

 Thus in a herd of cattle, the coupling between members is much 

 looser than the couplings within one member and between its parts 

 (e.g. between its four limbs); and the four limbs are not coupled as 

 closely to one another as are the molecules within one bone. Thus 

 if some portion of the totaUty is marked out as T, the chief source 

 D of disturbance is often other systems that are loosely coupled to 

 r, and often sufficiently similar to those in T that they might equally 

 reasonably have been included in it. In the discussion that follows, 

 through the rest of the book, this fact must be borne in mind : that 

 sometimes an equally reasonable demarcation of 7" and D might have 

 drawn the boundary differently, without the final conclusions being 

 affected significantly. Arbitrary or not, however, some boundary 

 must always be drawn, at least in practical scientific work, for 

 otherwise no definite statement can be made. 



13/4. When the system T is very large — when the organism as 

 regulator faces a very large and complex environment with limited 

 resources — there are various ways that may make regulation possible. 

 (If regulation is not possible, the organism perishes — an extremely 

 common outcome that must not be forgotten ; but this case needs no 

 detailed consideration.) 



Sometimes regulation may be made possible by a re-defining of 

 what is to be regarded as acceptable — by a lowering of standards. 

 This is a somewhat trivial solution, though not to be forgotten as a 

 possibility. 



Another possibility is to increase the scope and power of R, until 

 7?'s capacity is made adequate. This method must obviously never 

 be forgotten; but we shall give it no detailed consideration. Let 

 us consider more fully the interesting case in which the regulation, 

 apparently most difficult or impossible, is actually possible. 



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