170 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



no more than this when he interposes between the flying 

 atom and the eye a somewhat more complicated apparatus, 

 consisting of an ionisation chamber together with a galva- 

 nometer; only in this case the way is somewhat longer. All 

 investigation of nature depends upon an enlargement of our 

 senses of this description." 1 Theories, therefore, are, like 

 microscopes, instruments for exploring nature; consequently, 

 both the mental operation required in devising and using a 

 theory, and the end-result of such an operation must be 

 properly interpreted; the operation is not one of invention 

 but simply one of exploration, and the result of the operation 

 is not a creation but simply a datum. 



The contemporary scene in the philosophy of science is 

 characterized by more or less heated controversies between 

 the exponents of the various theories discussed in this chap- 

 ter. Of these conflicts the most sharply defined is that 

 between the positivists and the realists. The antagonism 

 between the extreme and the moderate positivists cannot 

 become intense, for the differences between the two positions 

 are essentially relative. The absence of rationalistic theories 

 of scientific concepts, to which reference was made earlier 

 in the chapter, is, perhaps, not surprising; science is so 

 obviously empirical in spirit and method that a rationalistic 

 explanation seems hardly plausible. Yet it is not altogether 

 untrue to say that constructionalism, conventionalism, and 

 logical positivism are the rationalisms of modern scientific 

 theory. All of these positions deny the necessity for any 

 conception of the a priori; yet it is significant that in these 

 theories the knowing operations function essentially in the 

 place of the a priori. The knowing operations — abstraction, 

 idealization, definition, linguistic invention and manipula- 

 tion — are not, according to the upholders of these points of 

 view, themselves determined by the character of the data; 

 they are imposed by the mind and become techniques by 

 which the knowing activities are fostered and developed. 

 They function, therefore, as something which must be given, 



1 Ibid., pp. 28-29. 



