13/11 AN INTRODUCTION TO CYBERNETICS 



Our treatment of it, while losing nothing in precision, must be 

 very broad — that is to say, abstract — for, as biologists, we want to 

 consider machines of far wider type than those of steel and brass. 

 Within the formula 



Entity Q designs machine M 



we want to include such cases as 



(1) The genes determining the formation of the heart. 



(2) A mechanic making a bicycle. 



(3) One part of the brain determining the internal connexions in a 

 nerve-net. 



(4) A works-manager laying out a factory to get production going 

 along certain lines. 



(5) A mathematician programming an automatic computer to 

 behave in a certain way. 



What we shall be concerned with, if we hold to the cybernetic 

 point of view, is not the more obvious processes of shaping or 

 assembling pieces of matter, but with the less obvious questions of 

 what determines the final model, of how it comes to be selected. 

 We are interested in tracing long chains of cause and effect, so that 

 we can relate a set of possible initial causes to a set of final machines 

 issuing as consequence; as a telephone mechanic, with a cable of a 

 hundred wires, relates each one going in at one end to some one 

 coming out at the other. By treating the matter in this way we shall 

 find that certain quantitative relations must hold; on them we can 

 base the ideas of the last chapter. Throughout, we shall be exempli- 

 fying the thesis of D. M. MacKay: that quantity of information, as 

 measured here, always corresponds to some quantity, i.e. intensity, 

 of selection, either actual or imaginable. 



The concepts of selecting, designing, constructing, building (briefly, 

 in any way being responsible for the eventual appearance of) an 

 actual machine share a common property, when one identifies 

 and measures the varieties concerned in the process. What might 

 turn up as M has variety — an embryo might produce any one of 

 many forms of muscular blood-pump. In fact, the gene-pattern in 

 Lumbricus leads to the production of an earthworm's heart, the 

 gene-pattern in Rana leads to the production of a frog's heart, and 

 that in Homo to a man's heart. Control, by the gene-pattern over 

 the heart, is clearly involved. So too is regulation, for in whatever 

 state the molecules in Lumbricus happen to be initially (there being 

 variety in the possibilities), under the action of the gene-pattern the 

 variety disappears, and a heart of standard worm's form appears. 



252 



