168 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



Scientific realism insists that this view is not plausible. 

 The words of Bavink indicate clearly the attitude of the 

 realist. "The truth which we state in opposition to this 

 excessive criticism of hypotheses is this, that precisely those 

 elements of the 'explanatory hypothesis' found by hypo- 

 thetical and speculative means form the truest and most 

 valuable contributions to knowledge made by science. Far 

 from being mere aids to work, pictures, models or the like, 

 they are in truth the most important matter, and contain 

 exactly that around which the whole of investigation turns." 1 

 "Atoms are just as real things as cannon balls or grains of 

 sand, as waves on water or mountains" 2 Reasons can be 

 given "which have forced present day physics and chemistry 

 to recognize the real existence of atoms and molecules as an 

 undoubted fact." 3 "The whole question of the physics of 

 today turns about the question: What is the atom? No 

 one asks any longer: in what respects do things behave 

 'as if they consisted of atoms?" 4 



Bavink develops his position by pointing out two im- 

 portant kinds of theories. First there are those which may 

 be called "elaborative." 'Their characteristic is that they 

 contain practically no hypothetical elements; the funda- 

 mental assumptions in them . . . are themselves data of 

 experience. ... If the word theory is understood as the 

 logical arrangement of a large number of single laws to 

 form a closed system of reasons and consequences, these 

 examples from physics are without doubt patterns for such 

 theories. Even philosophers who are not positivists will 

 have no objection to make to this statement." 5 But there 

 is another class of theories called "explanatory," and il- 

 lustrated by the atomic theory. 'The characteristic of this 

 kind of theory is that the desired logical connection and 

 unification of the facts is only reached on the basis of a 

 speculative assumption, which is described as the hypothesis 

 upon which the theory is based." 6 "A physical hypothesis 



1 The Natural Sciences, p. 38. 



2 Ibid., p. 29. 



3 Ibid., p. 19. 



* Ibid., pp. 37-38. 



5 Ibid., p. 34. 



6 Ibid., p. 34. 



