EXPLANATORY SCIENCE 207 



nor propositions having a maximum of truth and a minimum 

 of necessity; on the contrary science is seeking propositions 

 having a fair amount of both necessity and truth. 



This goal can be attained if one recognizes that the ra- 

 tional sciences contain both empirical propositions and those 

 other propositions which have been formulated for the 

 purpose of explaining the descriptive propositions. Rational 

 sciences are simply empirical sciences which have expanded 

 into the realm of the theoretical. The theoretical proposi- 

 tions cannot be taken away from the total science in which 

 they occur, for apart from this setting they become purely 

 arbitrary, and responsible only to the imagination for both 

 meaning and truth. In the context of their origin, however, 

 they retain responsibility to the empirical propositions; they 

 are both meaningful and true to the extent to which one may 

 deduce from them propositions capable of empirical verifica- 

 tion. All of the entities of the so-called rational sciences, 

 therefore, must be considered merely as hypotheses in terms 

 of which empirical propositions are to be explained, and 

 from which further empirical propositions are to be derived. 

 This seems to be the status of all propositions about perfect 

 triangles and circles, frictionless motion and ideal gases, i.e., 

 they refer to hypothetical events whose character is to be 

 determined by the events which they are called upon to 

 explain. It is unfortunate that when a descriptive science 

 becomes explanatory the interest of the investigator shifts 

 from the empirical propositions to the hypotheses. There is 

 reason for this shift of interest since the empirical proposi- 

 tions can all be deduced from the hypothesis and hence need 

 not be attended to explicitly. But what should be emphasized 

 is that the empirical propositions cannot be deduced unless 

 there is admitted into the postulate system a further proposi- 

 tion which states the relation of the ideal entities to the 

 actual entities. Apart from this there can be no "applica- 

 tions" of the postulate system, and it becomes arbitrary. 



(2) An explanatory science also claims to contain symbols 

 for those less clearly given events which are required for 



