108 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



Is an object changed by being moved about? On the one 

 hand, the presumption is that a simple change of location — 

 either of space or of time — does not modify an object in an 

 appreciable manner; where or when an object exists is not 

 an important fact about it. Though such a change would 

 bring about an alteration in the location of the appear- 

 ances it would presumably involve no modification in the 

 object itself. But, on the other hand, it must be recognized 

 that change in location is inseparable practically from change 

 in events; space and time are relations not merely between 

 empty points but between objects which may act causally 

 on one another. Change in location amounts practically to 

 change in environment, and this is often of great significance. 

 A piece of metal in a magnetic field is not the same as a 

 piece of metal outside of such a field, and if Julius Caesar 

 were alive today he would be a different man. The issue 

 cannot be settled by asking whether the operation is per- 

 formed on the object or on its physical medium, for often 

 the same result may be brought about either by moving 

 the object into a new medium or by setting up a new en- 

 vironment about the object. The dispute is not important 

 so long as one recognizes the intimate association between 

 position and causal influences. One of the important ad- 

 vantages of the laboratory is that it permits one to place 

 objects in situations in which he has a more or less complete 

 control over possible disturbing factors. 



In a great many situations, however, change of location 

 cannot be brought about in nature. Change of temporal 

 location is, except in a very limited sense, impossible. One 

 cannot reenact history, nor can one transport himself back 

 into the past. The possibilities of change in spatial location 

 are somewhat more extensive, though even here there are 

 definite limitations. Man cannot bring the stars down to 

 earth, nor can he travel far either above or beneath the 

 surface of the globe. Hence his information about certain 

 kinds of events is largely indirect in character, and occurs 

 through the instrumentality of other events. The inter- 



