200 THE LIMITATIONS OF SCIENCE 



he finds he must distinguish between different kinds, 

 and must warn us against their indiscriminate use: 

 " It is important not to multiply hypotheses beyond 

 measure, and to make them only one after the other. 

 If we construct a theory based on a number of hypoth- 

 eses, and if experiment condemns it, which of our 

 premises is it necessary to change? It will be impos- 

 sible to know. And inversely, if the experiment 

 succeeds, shall we believe that we have demonstrated 

 all the hypotheses at once ? " 



This is excellent advice, but when he makes hypoth- 

 eses, he does not heed his own warning and neither 

 does anyone else. Imagine a physicist saying to 

 another, yours is dead, now let me have a turn 

 with one. But let us follow Poincare's classification 

 further : 



" There are first those which are perfectly natural 

 and from which one can scarcely escape. It is diffi- 

 cult not to suppose that the influence of bodies very 

 remote is quite negligible. . . . They are the last that 

 ought to be abandoned. 



" There is a second class of hypotheses, that I shall 

 term neutral. In most questions the analyst assumes 

 at the beginning of his calculations either that matter 

 is continuous or, on the contrary, that it is formed of 

 atoms. He might have made the opposite assumption 

 without changing his results. He would only have 

 had more trouble to obtain them ; that is all. If, then, 



