Preface to the Second Edition 



At the time when this book was first written, information theory 

 was just beginning to be known. Since then its contribution to 

 our understanding of the logic of mechanism has been so great 

 that a separate treatment of these aspects has been given in my 

 Introduction to Cybernetics * (which will be referred to in this book 

 as /. to C). Its outlook and methods are fundamental to the 

 present work. 



The overlap is small. I. to C. is concerned with first principles, 

 as they concern the topics of mechanism, communication, and 

 regulation; but it is concerned with the principles and does not 

 appreciably develop their applications. It considers mechanisms 

 as if they go in small discrete steps, a supposition that makes their 

 logical properties very easy to understand. Design for a Brain, 

 while based on the same principles, mentions them only so far as 

 is necessary for their application to the particular problem of the 

 origin of adaptive behaviour. It considers mechanisms that 

 change continuously (i.e. as the steps shrink to zero), for this 

 supposition makes their practical properties more evident. It has. 

 been written to be complete in itself, but the reader may find 

 /. to C. helpful in regard to the foundations. 



In the eight years that have elapsed between the preparations 

 of the two editions, our understanding of brain-like mechanisms 

 has improved immeasurably. For this reason the book has been 

 re-arranged, and the latter two-thirds completely re-written. 

 The new version, I am satisfied, presents the material in an alto- 

 gether clearer, simpler, and more cogent form than the earlier. 



The change of lay-out has unfortunately made a retention of 

 the previous section-numberings impossible, so there is no cor- 

 respondence between the numberings in the two editions. I 

 would have avoided this source of confusion if I could, but felt 

 that the claims of clarity and simplicity must be given precedence 

 over all else. 



* Chapman & Hall, London : John Wiley & Sons, New York ; 3rd imp. 

 1958. Also translations in Czech, French, Polish, Russian and Spanish. 



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