184 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



but by inventing a fictitious substance or process or idea, in 

 terms of which the experiences can be expressed. A hy- 

 pothesis, in brief, correlates observations by adding some- 

 thing to them, while abstraction achieves the same end by 

 subtracting something." 1 



There is no doubt but that the distinction here expressed is 

 fundamental to the logic of science. But it requires two 

 important refinements before it can be inserted in a general 

 theory of scientific explanation. The first refinement appears 

 to be merely a matter of terminology, though it is more than 

 this. The method of abstraction should not be so called, 

 since abstraction is only one of several processes which play 

 essentially the same role in science. Abstraction is associated 

 with classification. But, as has already been seen, ordering 

 and correlating are two other important processes by which 

 data are put into manageable form. If classification is the 

 operation by which abstractions are obtained, one may say 

 equally well that ordering is the process by which series are 

 obtained, and correlating, or associating, is the operation 

 by which complexes are obtained. What is required, there- 

 fore, is a term broad enough in its significance to include 

 operations of classifying, ordering, and correlating. Pre- 

 sumably, "describing' would be precisely the word de- 

 manded, since these are all descriptive techniques. Certainly 

 the positivist would be well satisfied with this choice. For 

 him science consists of two methods — the descriptive, which 

 is the essential method of science, and the hypothetical, 

 which is dangerous and to be avoided at all costs. But for 

 the modified positivist and for the realist this term would 

 not be adequate; the essential feature of these methods is 

 that they involve the creation of entities by definite acts of 

 thought. Pure description never does this. In this connec- 

 tion Bavink's choice of the word "elaborative" to character- 

 ize these methods is particularly apt. Russell describes such 

 techniques as methods of "logical construction " ; they result in 



1 H. Dingle, Science and Human Experience (London: Williams and Norgate, 

 1931), pp. 22-23. 



