17/7 ANCILLARY REGULATIONS 



communication within the brain can clearly be necessary or 

 advantageous. 



17/6. A second reason why communication within the brain may 

 be desirable can be discussed rigorously only in the concepts of 

 /. to C, S. 7/7, but the reason can be sketched here. 



When a system is described, it starts by being a member of a 

 large class of possible forms; as each specification is added, so 

 does the class that it may belong to shrink. Start with a system 

 restricted only by having the states possible to it fixed at a certain 

 number. If now is added the further specification ' its diagram 

 of immediate effects contains all possible arrows ', the possibilities 

 in its fields are restricted only slightly. But had it been added 

 that the diagram contained few arrows, the possibilities in the 

 fields would have been restricted severely. 



Thus, other things being equal, the fewer the joins, the fewer 

 are the modes of behaviour available to the system. From this 

 point of view, extra connexions within the brain can be advan- 

 tageous, for they make possible a greater repertoire of behaviours. 



Another way by which the same fact can be seen is to consider 

 the reacting parts before they w r ere joined. The parameters used 

 in the joining must, before the joining, have had fixed values (for 

 otherwise the parts would not have been state-determined). Thus 

 before the joining each parameter must have been fixed at some 

 one of its possible values; after the joining the parameter would be 

 capable of variation as it was affected by the other part. With 

 the variation would have come, to the part, a corresponding 

 variety in its fields, and ways of behaving (S. 6/3). Thus joining, 

 by mobilising parameters that would otherwise be fixed, adds to 

 the variety of possible behaviours. 



It can now be admitted, without misunderstanding, that Figure 

 16/6/1 would have been more realistic with some connexions 

 drawn between the reacting parts. The presentation and dis- 

 cussion at S. 16/6, however, was simpler without them. 



17/7. If increased connexions between the reacting parts in the 

 organism bring in the two advantages just described, they also 

 bring in, as S. 16/4 showed, the disadvantage of lengthening, 

 perhaps to a very great degree, the time required for adaptation. 

 Doubtless there are even more factors to be reckoned in the 



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