88 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



be noted, are identical to those expressed in Chapter III 

 where cognition in general rather than perception was the 

 topic of discussion. It was found there, as it is now found 

 here, that knowledge is impossible unless there is (1) some- 

 thing which may be called direct awareness, and (2) some- 

 thing which may be called indirect awareness. The former 

 is required to make truth possible, and the latter to make 

 error possible. But one is now able to see more clearly 

 what this indirect or symbolic awareness is. The symbolic 

 function of mind is identical with its inferential function. 

 Symbols are the essential instruments by means of which 

 one extends the immediately given. Hence symbolic aware- 

 ness is an inferential awareness of something not immediately 

 given in direct awareness, but hinted at or suggested 

 with a greater or less degree of clarity. Many of my 

 "private" sense-data, which I know immediately, indi- 

 cate " public'' objects, and it is through the instrumen- 

 tality of symbols that I become aware of such objects. 

 The objects enter into my knowledge through symbols, 

 hence the symbols occupy an intermediary position between 

 the " private'' sense-data which are given immediately, 

 and the ''public' objects which these sense-data seem to 

 demand. 



SCIENTIFIC REALISM 



The correct understanding of the part which symbols 

 play in this general situation enables one to construct a 

 theory of perception which seems to be more adequate 

 than any of the three considered above. It may be called 

 scientific realism. Its fundamental claim is that the elements 

 of perception should be defined in terms of certain neutral 

 particulars, as in the case of positivism. But it argues that 

 the structure of perception is expressible only in terms of 

 complex relations between certain clusters of these neutral 

 elements. Hence its first problem is to show how these 

 elements become associated into groups which are called 

 objects of certain kinds. 



