110 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



more or less arbitrarily, a situation in which the physical 

 medium is presumed to produce a minimum of transforma- 

 tions. Then changes are introduced into the medium with a 

 view to determining how the appearances of the end-object 

 are affected by these modifications. Every new appearance 

 affords further insight into the character of the object. 

 Most important of these modifications are those which 

 involve the insertion into the medium of recording and 

 measuring devices, such as thermometers, ammeters, bal- 

 ances, micrometer screws, microscopes, telescopes, spectro- 

 scopes, phonographs, hydrometers, counting and sorting ma- 

 chines, clocks, and compasses. Other modifications include 

 manipulative techniques, such as applying meter bars to 

 objects, isolating objects from "disturbing' environmental 

 factors, changing illumination, and varying the position of 

 the observer. The function of these instrumental and 

 manipulative methods is to multiply and vary as greatly 

 as possible the appearances of the end-object to the observer. 

 If the object is the totality of its appearances, one learns 

 more about the object every time he discovers it under a 

 new manifestation. Hence it is to his advantage, in his 

 desire to explore the realm of nature, to increase the range 

 of possible appearances. If one limits the modifications to 

 such as are introduced through measuring instruments, then 

 he is justified in defining physical objects, in the words of 

 Eddington, as "schedules of pointer readings." x But if 

 one includes modifications which are not of this specific 

 kind, he cannot define physical objects so narrowly. It 

 seems better to employ the more general definition and to 

 say that a physical object is a schedule of its various ap- 

 pearances at different places and times and under the influ- 

 ence of controlled modifications in the intervening medium. 

 One of the most important of the transformations intro- 

 duced by the P-operators is the act of isolation. An iso- 

 lational act is the foundation not only of science but of 

 common sense as well. All observation is analytic and 



1 Nature of the Physical World, p. 259. 



