DESIGN FOR A BRAIN 22/14 



independent of A. Thus a wall of constancies (the B's null- 

 functions) between the systems A and C is sufficient to leave them 

 each state-determined and independent of the other. 



(2) Suppose the systems A and C are each found to be state- 

 determined and independent of one another; the whole is given 

 to be state-determined, and there is known to be no immediate 

 connexion from A to C or from C to A, but there is effective 

 connexion between A and B, and between C and B — what can 

 be deduced about the variables in B ? 



The lack of connexion between A and C shows that the canonical 

 representation must have the form of (1) above. With 



XA =fA(cCA, OCb) 



the A's can be state-determined only if all the i5's are constant 

 (not effectively functions of the time). So the 2?'s must be null- 

 functions. 



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