90 THE ANATOMY OF SCIENCE 



evidence have we that it is none of these proper- 

 ties, but the property which we call weight or 

 mass that determines equilibrium? 



It seems rather that we must define weight as 

 that characteristic of bodies which determines 

 balance under such circumstances. But are we 

 justified in making such a definition? Does it 

 not involve the experimental observation that if 

 A balances B and B balances C, then A balances 

 C ; or, in other words, that two weights equal to 

 the same weight are equal to each other? Often 

 in science we find empirical laws concealed in 

 what purports to be a definition. 



If we should proceed to analyze Archimedes' 

 various deductions we should find none of his 

 proofs entirely satisfactory; but is there any 

 such thing as absolutely rigorous proof? Is not 

 a proof only an attempt to render plausible 

 new statements by correlating them with others 

 that are already accepted? We may doubt 

 whether a scientist ever presents all of the evi- 

 dence which has led him to a new law or a new 

 theory. He probably is never aware of all his 

 reasons, or at least never aware of them all at 

 any one instant of time. Moreover, he often 

 suppresses some part which cannot be presented 

 with that formality which the fashion of the 



