DESIGN FOR A BRAIN 3/8 



3/8. These two examples, however, are mentioned only as 

 introduction; rather we shall be concerned with the nature of the 

 free-living organism within a natural environment. 



Given an organism, its environment is defined as those variables 

 whose changes affect the organism, and those variables which are 

 changed by the organism's behaviour. It is thus defined in a purely 

 functional, not a material, sense. It will be treated uniformly 

 with our treatment of all variables : we assume it is representable 

 by dials, is explorable (by the experimenter) by primary opera- 

 tions, and is intrinsically state-determined. 



Organism and environment 



3/9. The theme of the chapter can now be stated: the free- 

 living organism and its environment, taken together, may be 

 represented with sufficient accuracy by a set of variables that 

 forms a state-determined system. 



The concepts developed in the previous sections now enable us 

 to treat both organism and environment by identical methods, 

 for the same primary assumptions are made about each. 



3/10. As example, that the organism and its environment form 

 a single state-determined system, consider (in so far as the activities 

 of balancing are concerned) a bicycle and its rider in normal 

 progression. 



First, the forward movement may be eliminated as irrelevant, 

 for we could study the properties of this dynamic system equally 

 well if the wheels were on some backward-moving band. The 

 variables can be identified by considering what happens. Suppose 

 the rider pulls his right hand backwards: it will change the 

 angular position of the front wheel (taking the line of the frame as 

 reference). The changed angle of the front wheel will start the 

 two points, at which the wheels make contact with the ground, 

 moving to the right. (The physical reasons for this movement 

 are irrelevant: the fact that the relation is determined is sufficient.) 

 The rider's centre of gravity being at first unmoved, the line 

 vertically downwards from his centre of gravity will strike the 

 ground more and more to the left of the line joining the two 

 points. As a result he will start to fall to the left. This fall will 

 excite nerve-endings in the organs of balance in the ear, impulses 



36 



