144 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



sciences themselves are not sufficiently integrated to neces- 

 sitate an important and extensive revision should such occur. 

 In other words, these sciences are continually adapting 

 themselves to important discoveries, but the changes re- 

 quired are of a minor character and hence are not critical 

 events. 



(2) Descriptive science is non-explanatory. Unless this 

 statement is interpreted it may amount to a mere identity, 

 i.e., a statement that a descriptive science is descriptive. 

 Ordinarily the distinction between description and explana- 

 tion is formulated in terms of the respective questions which 

 they are designed to answer. Description answers the ques- 

 tion "How?" and explanation answers the question "Why?" 

 Descriptive science, then, symbolizes the way in which 

 events exhibit themselves and behave; explanatory science 

 symbolizes other events (or hidden features of the events 

 themselves) in terms of which this behavior is to be under- 

 stood. A simple formulation of the problem is to say that 

 explanatory science is concerned with the premises from 

 which the propositions of descriptive science may be deduced 

 as theorems. Hence when one explains he searches for 

 reasons, grounds, or causes, and the relation between any 

 such entities and the events which they explain is that of 

 logical implication. It follows that a descriptive science 

 cannot explain, for its structure is not logical. As was 

 pointed out, its propositions are independent of one another, 

 and therefore in no sense derivable from one another. Hence 

 descriptive science cannot answer the question "Why?" 

 but must confine its activity to the statement of the mere 

 "How?' The laws of gravitation will not state why bodies 

 fall, but how they fall; the principles of natural selection 

 will not state why organic forms develop, but how they 

 develop. 



It follows that facts for descriptive science are simply 

 brute facts. One knows that they exist, but he does not 

 know why. Nature might have chosen to be otherwise. 

 Every fact in descriptive science suggests its own alternative. 



