130 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



and rests entirely on those facts, without corroboration 

 from other branches of knowledge. It is contrasted with 

 generalized and theoretical knowledge, which embraces many 

 series of facts under a few comprehensive principles, so that 

 each series serves to throw light upon each other series of 

 facts. Just as, in the map of a half-explored country, we see 

 detached bits of rivers, isolated mountains, and undefined 

 plains, not connected into any complete plan, so a new 

 branch of knowledge consists of groups of facts, each group 

 standing apart, so as not to allow us to reason from one to 

 another." x 



Allowing this to serve as a preliminary, one may attempt 

 to discuss somewhat more systematically the features of 

 descriptive science. Since it is a body of symbols, and every 

 symbol has, as was shown in Chapter IV, extensional and 

 intensional relations, one may suggest the examination of 

 descriptive science from the point of view of (a) extension, 

 i.e., the character of its reference to events, and (b) inten- 

 sion, i.e., the character of the interrelations of the symbols 

 among themselves. 



EXTENSIONAL FEATURES OF DESCRIPTIVE SCIENCE 



Extensionally every descriptive science aims (1) to repre- 

 sent the most clearly given events, by symbolizing the more 

 obvious of (2) their classificatory, (3) their serial, and 

 (4) their correlational features. The precise meaning to be 

 attributed to each of these aspects is important, and warrants 

 a more detailed consideration. 



(1) Since every descriptive science is presumably a linguis- 

 tic system, the representation involved in any such science 

 is that kind which is peculiar to word symbols. (Numbers 

 and other mathematical symbols may here be considered 

 as condensed word symbols.) No word symbol, as has al- 

 ready been seen, portrays its referent in any direct or pic- 

 torial sense. Words do not look or sound like the events to 

 which they refer. But they have the capacity, by virtue of 



1 Ibid., p. 526. 



