CONCLUSION 



The measure of success of a predictive theory depends upon at 

 least three factors: the simplicity of the theory, the range of its appli- 

 cations, and its accuracy. It is quite possible for both of two incom- 

 patible theories to be in common use when one is much simpler, the 

 other more extensive or more exact in its applications. This is the 

 case with the gravitational theories of Newton and Einstein. While 

 the measure of a theory's simplicity is evident to any competent read- 

 er, the test of its range and accuracy must be the work of the experi- 

 menter. Thus the success, and also the improvement, of a scientific 

 theory rests quite as much upon the experimenter as upon the theorist. 



The theories presented in this monograph point two ways. On 

 the one hand, they provide for the prediction of behavior. On the 

 other hand, they presuppose the presence of specific anatomical struc- 

 tures. Such a theory might give a very accurate representation of 

 behavior without necessarily deriving from a correct representation 

 of the actual mediating stucture. If so, it is no less useful in the one 

 direction for having failed in the other, though it is to be expected 

 that further investigation should lead to a theory that is more success- 

 ful in both respects. 



The advantage of having a theory lies not only in the fact that 

 the theory, if it should prove accurate in its predictions, provides 

 just that much of an increase to our fund of knowledge, or increases 

 by just that much our command over nature. A well-formulated the- 

 ory, in addition, gives direction and meaning to experimental work 

 even when the experiments fail to confirm the theory, since the fail- 

 ure must occur in a certain direction, by a certain amount, and must 

 therefore provide the necessary, hitherto lacking, background for the 

 construction of a better theory. 



Furthermore, theoretical organization gives unity and coherence 

 to the otherwise multifarious and apparently disparate phenomena 

 of observation. It has been remarked (Williams, 1927) that the ele- 

 mentary physics textbooks have diminished considerably in size dur- 

 ing recent decades in spite of the tremendous increase in our physical 

 information, just because details formerly treated separately are more 

 and more brought together as special cases of a few general princi- 

 ples. In our brief account we have indicated here and there (cf. in 

 particular chap, vi) how quite different forms of response could be 

 mediated by structures of the same kind and are thus to be subsumed 

 under the same principle. Doubtless many other instances could be 

 found, and will be as the work progresses. Thus it is to be hoped that 

 as the formulations are improved the same progress will be observ- 



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