160 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



about a scientific theory is . . . whether it is logically co- 

 herent and how far it is adequate for the purpose of repre- 

 sentation. . . . Natural Science postulates, as a working 

 hypothesis, only that the perceptual complex is such that 

 tracts of it are capable of conceptual description by scientific 

 schemes. It does not require any postulate as to detailed 

 systems of relations or of entities within that perceptual 

 complex, or within any supposed reality behind that complex, 

 which shall account for the fact that the working hypothesis 

 has proved successful." 1 It is unnecessary for the purposes 

 of Natural Science "to make the assumption that a single 

 law has a precise correspondence with a single definite set 

 of relations which actually subsist in nature." 2 



Hobson's position can be characterized, therefore, as a 

 modified positivism, which insists that data are only the 

 raw material of knowledge. These data must be worked 

 over by an active mind and transformed into idealized 

 symbols, which are then combined into symbolic schemes. 

 Many elements of such schemes have lost all direct cor- 

 respondence with the data from which they were derived, 

 hence the system as a whole has no immediate representa- 

 tive value. It is therefore no longer descriptive, but is 

 considered as "applicable" in a somewhat less direct sense. 

 In addition to applicability it must have internal consistency, 

 relative simplicity, and predictive value. It is the task of 

 science to construct a system of symbols of this kind. 



CONVENTIONALISM 



Conventionalism may be described as a more extreme 

 constructionalism. It is distinguished from the latter in its 

 recognition of the increased importance of the knowing 

 operations. If scientific concepts are merely constructed 

 out of the raw material given in perception, they are still 

 related to it in the sense that they have been derived by 

 describable techniques ; abstraction and idealization are oper- 

 ations of transformation, but one can, by retracing the 



i Ibid., p. 59. 2 Ibid., p. 26. 



