THEORIES OF SCIENTIFIC CONCEPTS 169 



is the presumption of the existence of a general state of affairs, 

 lying at the back of certain phenomena which are matters of 

 experience, and allowing the phenomena in the field of facts 

 in question to be deduced qualitatively and quantitatively (math- 

 ematically) from the presence of the said state of affairs and 

 its assumed laws." l This is "a supposition which was 

 arrived at by purely speculative methods," 2 but it requires 

 the physicist to admit that "molecules and light waves, 

 fields and their tensors, have just the same kind of reality 

 as stones and trees, plant cells or fixed stars." 3 



Some of Bavink's statements lead one to believe that he 

 would insist on this realistic attitude not only toward 

 hypotheses but also toward all idealizations and even to- 

 ward concepts themselves. In his criticism of convention- 

 alism, for example, he argues that idealizations cannot be 

 the result of arbitrary acts of mind, for "both the matter 

 and the manner of neglect is completely dictated to us by 

 the object; . . . the world is so constructed, that it can be 

 known, by means of rational concepts, in rational judgments 

 (laws) of increasing approximation, and it prescribes the path 

 of these approximations to our understanding" 4 "Even 

 concepts such as plant and animal, or oak or beech, have 

 not been put into nature by us or invented in order to make 

 it more easy for us to grasp; they are forced upon us by an 

 objective something that was there long before men with 

 power of conceptual thought existed." 5 



Such quotations as these indicate the legitimacy of as- 

 serting — as was suggested early in the chapter — that for 

 realists the knowing operations are operations of discovery 

 or of exploration rather than of construction or invention. 

 When we look at cells through a microscope "we do not 

 see the cells directly in the literal sense. However, no one 

 seriously doubts that the picture seen in the microscope is 

 in general similar to reality, and even geometrically similar, 

 if we leave distortion out of account, which itself can be 

 exactly calculated. ... In principle, Rutherford is doing 



1 Ibid., p. 42. 2 Ibid., p. 35. 3 Ibid., p. 243. 4 Ibid., p. 233. 6 Ibid., p. 234. 



