PREFACE 



It is divided into three parts. 



Part I deals with the principles of Mechanism, treating such 

 matters as its representation by a transformation, what is meant by 

 "stability", what is meant by "feedback", the various forms of 

 independence that can exist within a mechanism, and how mechan- 

 isms can be coupled. It introduces the principles that must be 

 followed when the system is so large and complex (e.g. brain or 

 society) that it can be treated only statistically. It introduces also 

 the case when the system is such that not all of it is accessible to 

 direct observation— the so-called Black Box theory. 



Part II uses the methods developed in Part I to study what is 

 meant by "information", and how it is coded when it passes through 

 a mechanism. It applies these methods to various problems in 

 biology and tries to show something of the wealth of possible 

 applications. It leads into Shannon's theory; so after reading this 

 Part the reader will be able to proceed without difficulty to the study 

 of Shannon's own work. 



Part III deals with mechanism and information as they are used in 

 biological systems for regulation and control, both in the inborn 

 systems studied in physiology and in the acquired systems studied in 

 psychology. It shows how hierarchies of such regulators and 

 controllers can be built, and how an amplification of regulation is 

 thereby made possible. It gives a new and altogether simpler 

 account of the principle of ultrastability. It lays the foundation 

 for a general theory of complex regulating systems, developing 

 further the ideas of Design for a Brain. Thus, on the one hand it 

 provides an explanation of the outstanding powers of regulation 

 possessed by the brain, and on the other hand it provides the 

 principles by which a designer may build machines of like power. 



Though the book is intended to be an easy introduction, it is not 

 intended to be merely a chat about cybernetics — it is written for those 

 who want to work themselves into it, for those who want to achieve 

 an actual working mastery of the subject. It therefore contains 

 abundant easy exercises, carefully graded, with hints and explanatory 

 answers, so that the reader, as he progresses, can test his grasp of 

 what he has read, and can exercise his new intellectual muscles. A 

 few exercises that need a special technique have been marked thus: 

 *Ex. Their omission will not affect the reader's progress. 



For convenience of reference, the matter has been divided into 

 sections; all references are to the section, and as these numbers are 

 shown at the top of every page, finding a section is as simple and 

 direct as finding a page. The section is shown thus: S.9/14 — 

 indicating the fourteenth section in Chapter 9. Figures, Tables, and 



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