152 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



phase of present or past life therein, has been examined, 

 classified, and coordinated with the rest, then the mission 

 of science will be completed." l The essential instrument 

 in this task is the concept, by which thought classifies im- 

 pressions, "analyses or simplifies their characteristics, and 

 forms general notions of properties and modes." 2 For 

 example, the concept of an object is simply a convenient 

 shorthand device for associating present sense-impressions 

 with stored or memory impressions. All of science, in fact, 

 is inspired by this spirit of economy. It is searching a brief 

 description, a mental resume of the universe. Pearson 

 quotes with approval Kirchhoff's definition of mechanics: 

 "Mechanics is the science of motion; we define as its object 

 the complete description in the simplest possible manner of 

 such motions as occur in nature." 3 



But what can be said about such things as atoms, mole- 

 cules, geometrical surfaces, particles, and absolute rigidity? 

 Science contains symbols for such entities, and every logic 

 of science must account for them. Pearson's answer is clear. 

 In the process of constructing concepts to express in sim- 

 plified form the relationships and sequences of phenomena 

 "we often analyse the material of sense-impressions into 

 elements which are not themselves capable of forming dis- 

 tinct sense-impressions; we reach conceptions which are not 

 capable of direct verification by the senses; that is to say, 

 we can never, or at least we cannot at present, assert that 

 the elements have objective reality. Thus physicists reduce 

 the groups of sense-impressions which we term material 

 substances to the elements molecule and atom, and discuss 

 the motion of these elements, which have never been, and 

 perhaps never can become, direct sense-impressions. No 

 physicist ever saw or felt an individual atom." 4 Hence 

 there is no doubt that there are at least symbols of this kind 

 in science. 



But what is their function? Here, again, Pearson is quite 

 clear. They do not explain, for in science there is no ex- 



1 Ibid., pp. 12-13. 2 Ibid., p. 46. 3 Ibid., p. 115. * Ibid., p. 95. 



