Chapter II 



RELATIVITY 



Einstein's Principle. The modest observer mentioned in 

 the first chapter was faced with the task of choosing 

 between a number of frames of space with nothing to 

 guide his choice. They are different in the sense that they 

 frame the material objects of the world, including the 

 observer himself, differently; but they are indistinguish- 

 able in the sense that the world as framed in one space 

 conducts itself according to precisely the same laws 

 as the world framed in another space. Owing to the 

 accident of having been born on a particular planet 

 our observer has hitherto unthinkingly adopted one of 

 the frames; but he realises that this is no ground for 

 obstinately asserting that it must be the right frame. 

 Which is the right frame? 



At this juncture Einstein comes forward with a sug- 

 gestion — 



"You are seeking a frame of space which you call 

 the right frame. In what does its rightness consist?" 



You are standing with a label in your hand before a 

 row of packages all precisely similar. You are worried 

 because there is nothing to help you decide which of 

 the packages it should be attached to. Look at the label 

 and see what is written on it. Nothing. 



"Right" as applied to frames of space is a blank label. 

 It implies that there is something distinguishing a right 

 frame from a wrong frame; but when we ask what is 

 this distinguishing property, the only answer we receive 

 is "Rightness", which does not make the meaning clearer 

 or convince us that there is a meaning. 



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