YERIFICATORY TECHNIQUES 215 



embryonic. This is the stage in which the science from which 

 the theory is to emerge is still at the descriptive level. The 

 techniques employed up to this point have been directed 

 mainly at getting the data through the introduction of 

 physical, physiological, and psychological operators, and 

 describing the data through the introduction of classifica- 

 tion, ordering, and associating. Only the most obvious 

 events are attended to. At this level there is no mention of 

 hypotheses or theories, though the foundation upon which 

 the theoretical structure will be built is being established. 



The second stage is one in which there is recognition of the 

 insufficiency of mere description. It is seen that the task of 

 science is not merely the description of that which is ob- 

 viously given, but the explanation of this in terms of some- 

 thing which is less obviously given. Hence it is admitted 

 that the problem of science lies in the more or less imagina- 

 tive extension of the given and the resulting introduction 

 into science of conjectural, hypothetical, and theoretical 

 entities. The essential technique which is employed at this 

 stage is the method of construction. It recognizes the danger 

 in the use of the uncontrolled imagination, and endeavors to 

 keep the explanatory conceptions as close as possible to the 

 range of data. It attempts, so far as this is feasible, to derive 

 explanatory conceptions from the data. The methods of 

 abstraction and of concretion are the two most important 

 techniques at this stage; they aim to give to the conjectural 

 notion only such content as is demanded by the data. Hence 

 they are considered to be essentially elaborative, and not 

 sharply differentiated from the strictly descriptive tech- 

 niques. 



The third and fourth stages constitute the most significant 

 stages in the development of a theory. For only at these 

 levels does the theory become truly explanatory. The 

 theory explains because it implies propositions descriptive 

 of the data. Hence the data are explained if there can be 

 found the required propositions making assertions about 

 hypothetical and conjectural entities, and of such a char- 



