THEORIES OF SCIENTIFIC CONCEPTS 167 



the more traditional positivists such as Hobson and Pearson. 

 Carnap's formal sentences are those types of symbols which 

 are determined simply linguistically. But language itself is 

 simply a technique of knowing, a set of rules formulated 

 and agreed upon by which symbolic devices may be con- 

 structed and transformed. Hence one may say that formal 

 symbols are such that their meaning and truth — in the only 

 sense in which they can be said to have meaning and truth — 

 are determined rather by the methods of knowing, i.e., the 

 operations, than by that which is known, i.e., the data. They 

 have no content — except linguistic content. They do not 

 therefore make assertions — except about the linguistic tech- 

 niques which are employed in all knowing. It seems safe 

 to say, therefore, that Carnap's position represents an ex- 

 treme in the class of what were characterized at the begin- 

 ning of the chapter as "modified positivisms." In his case, 

 however, the symbols which are not directly descriptive 

 cease to be even indirectly descriptive; they are exhaustively 

 determined by the knowing operations concerned with the 

 formation of symbols, and not determined at all by data. 



SCIENTIFIC REALISM * 



Common to all positivisms, both of the strict type and of 

 the modified type, is the attitude which Bavink calls 'hy- 

 potheseophobia." For the purer forms of positivism this 

 attitude expresses itself in a definite rejection of hypothetical 

 and theoretical entities of all kinds except in so far as they 

 serve merely as classificatory concepts. Mach expresses 

 the hope that atoms will finally disappear from the theory 

 of heat. Modified positivism admits such entities, but 

 somewhat reluctantly; it insists that they have only a con- 

 ceptual status and are therefore to be called constructs, 

 conventions, and fictions. Characteristic among such beliefs 

 is that of Vaihinger, who insists that the proper attitude 

 of the scientist is one of "as if"; atoms do not exist, but 

 nature behaves just "as if" they did. 



1 This is not, of course, to be confused with "scientific realism" as a theory of 

 perception, developed in Chapter V. 



