114 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



flattens it slightly; a thermometer, unless of exactly the 

 same temperature as the object whose heat is to be recorded, 

 modifies its temperature and consequently does not indi- 

 cate accurately the character of the phenomenon which it 

 presumes to measure. Hence one is obliged to remain satis- 

 fied with a relative neutrality. In the second place, the 

 system which is made up of the event and the instrument 

 must itself be a relatively isolated complex. "Every good 

 experimenter has to compensate for all sorts of extraneous 

 effects that enter into his experiments — slight changes in 

 temperature in the room during the progress of the test, 

 draughts, vibration of the building, heat radiation from the 

 body of the experimenter himself, and so on." * Finally, 

 no value obtained through an operation of measurement 

 can be divorced from the technique used in obtaining it. 

 Numbers are always applied values and one should never 

 lose sight of the character of the application in each specific 

 case. This implies that in measurement acts one should recall 

 what he has done, and in the employment of measuring 

 devices one should be aware of the principles according to 

 which the instrument is constructed and operates. 



An important problem, which may be merely mentioned 

 at this point, arises in the attempt to give measurement a 

 sound theoretical foundation. Is the meaning of any physical 

 concept exhausted when one has stated the techniques by 

 which its measured value may be ascertained? Does time 

 mean simply clock readings? Does space mean simply 

 numbers on scales? Does force mean simply readings on the 

 indicators of balances? More detailed examination of the 

 theory which is implied in an affirmative answer to these 

 questions will be made in connection with the analysis of 

 the basic concepts of the sciences in Part II. Probably the 

 issue can be decided only by examining completely the 

 techniques which are involved in the measurement of any 

 given event, and determining whether the methods of con- 

 structing and calibrating instruments, as well as the methods 



1 H. Levy, Universe of Science, pp. 49-50. 



