218 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



clear that a theory is not properly such until it has under- 

 gone at least a minimum of verification; inadequacies in the 

 theory can be detected only by examining the predictions 

 in the light of the facts, hence a false theory may be said to be 

 one which has developed improperly or incompletely. This 

 would seem to argue for the thesis that verification of a 

 theory is the fifth stage in its development. But the move- 

 ment of verification, on the other hand, is quite strictly the 

 reverse of the movement of discovery. The movement of 

 discovery is essentially a movement from data to symbols, 

 from the clearly given to the obscurely given; while the 

 movement of verification is essentially a movement from 

 symbols to data, from the obscurely given to the clearly 

 given. The former is a leap in the quagmires of conjecture, 

 the latter is a return to the hard ground of fact. The former is 

 inductive, receiving its motivation from insight and imagina- 

 tion, and carried on most readily by those types of mind 

 excelling in spontaneity and suggestion; the latter is deduc- 

 tive, deriving its impulse from criticism, and pursued most 

 actively by those types of mind excelling in logical rigor. 

 Hence the movements seem to be different in kind and to 

 offer support for the thesis that in the movement of verifica- 

 tion the attitude and direction of the mind have been changed. 

 In the broadest sense of the term, verification may be 

 considered as a double movement. It involves, first, the 

 actual drawing of the implications from the hypothesis after 

 it has been expanded through the hypothetical method. This 

 may be called the movement of prediction. But it involves also 

 the act by which the implied notions are compared either with 

 existing data or with data which are capable of creation through 

 experimental methods. This may be called the movement of 

 confirmation. Each of these will be discussed briefly. 



PREDICTION 



The movement of prediction is one of deduction, and, as 

 such, seems to offer no significant difficulty. There are 

 recognized techniques of formal deduction. Hence the prob- 



