50 SCIENCE (and common sense) 



^aws of nature." These laws are still, however, humanly created and 

 expressed laws, not unmarked by the characteristics of their creators. 

 By no stretch of imagination can such laws be considered mere "eco- 

 nomic descriptions" of obser\^ables, or the like. At first sight we may 

 conceive the possibility of easily arriving at, say, the law of the lever, 

 purely on the basis of observation. Imagine how we might try to do 

 so— assuming ourselves untutored savages who, however preposter- 

 ously, have a modern outlook, a taste for systematic study, and some 

 knowledge of elementary mathematics. 



The law of the lever. Our casual experience of moving boulders 

 with a wooden beam is an inadequate foundation for discovery of the 

 law of the lever. In the opening scene of this little fantasy we are 

 found sitting in front of our cave, manipulating an assembly of a 

 light, rigid, straight bar (if not a titanium rod, perhaps a fragment 

 of a giraflFe's shinbone), a sharp horizontal support (if not an agate 

 knife-edge, then a suitably chipped rock outcropping), and an as- 

 sortment of objects. Do not ask now ivhy we should concern ourselves 

 with this curious array of things in the first place: we are too busy 

 discovering the law of the lever. 



We hang two objects, arbitrarily chosen, at arbitrarily chosen posi- 

 tions along the bar. Sliding the bar along the support, F, we discover 

 one curiously unique position between the points of suspension of 

 the two objects. When this position falls directly over F, the bar re- 

 mains at rest in a horizontal plane— after a series of oscillations we 

 agree to ignore as "irrelevant." When this state is attained we say: 

 *'The system is in balance." Without making any other change, we 

 now add a third object to one of those already suspended. We find 

 that the system then is no longer in balance. But balance can be re- 

 stored, we find, by shifting the bar along the support F in the direc- 

 tion that approaches the added object to F. Continuing such trials, 

 we find that, by suitable placement on the support F, we can bring 

 the system into balance even when we have but one object on one 

 side of F and a great many objects, suspended together, on the other 

 side. 



Already we have passed far beyond "pure observation." Into our 

 report have crept distinctly conceptual elements like side, support, 

 one and many, horizontal, system, etc. Moreover, if we are still rea- 

 sonably close to pure observations, we are also painfully far from 

 having gotten anywhere with them. Clearly we are not going to get 



